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利奈唑胺（LINEZOLID，ZYVOX）说明书

 

 

fda正式批准了第一个新一类抗菌药物zyvox。可用来治疗vref（耐万古霉素微肠球菌）引起的多重感染，血源性感染，医源性肺炎，严重并发性皮肤感染，以及耐甲氧西林的金葡球菌引起的感染。

微肠球菌和mrsa（耐甲氧西林金葡球菌）引发的严重感染是医疗上一个严重的问题。这类微生物通常对多种抗生素有很强的耐药性。长期以来万古霉素一直是治疗这类感染的最后手段。1989年，美国报道了有关vref（耐万古霉素微肠球菌）的第一个耐药性案例。从此。有关vref耐药性的报道层出不穷。人类对 vref感染病人的治疗也越来越显得无能为力。

zyvox是在美国和全世界批准应用的?f唑烷酮类人工合成抗生素的第一个药物。同时也是近40年来第一个进入美国市场用来治疗mrsa感染的药物。

经过对4000多例病人严格控制的临床试验证明zyvox在治疗严重感染方面有确切的疗效。对145例vref感染病人，包括各种有并发性严重腹部感染.并发性皮肤重度感染，尿路感染。.和不明原因的菌血症病人每12小时服用600-200mg的治疗观察和量效观察研究证明。zyvox抗感染的治愈率在高剂量时达到67%，低剂量为52%。

同时在对400多例病人进行的临床试验中发现。 zyvox治疗医源性肺炎（包括mrsa耐甲氧西林金葡球菌引起的感染性肺炎）同万古霉素一样有效.在对太约800多病人进行的临床对照实验中发现，与服用苯唑西林和双氯西林的临床对照组比较，zyvox对包括由mrsa引起严重并发性皮肤感染和软组织感染也有较好的疗效。

临床试验研究报道zyvox的主要副反应是头痛,恶心,腹泻,呕吐.同时引起血小板数量的减少。

zyvox与含伪麻黄碱或盐酸去甲麻黄碱的非处方类药合用将导致血压的升高。因此病人同时服用这类药物时必须先向医生说明。

考虑到抗生素的不合理应用导致耐药菌日益增多，zyvox的制造商phaumacia和upjohn公司希望开始阶段主要在医院或有严格的监护条件下使用zyvox来治疗严重感染.门诊医生在使用zyvox时应该斟酌选用。

根据在2000年3月24日的委员会议上公布的临床试验结果,fda 遵照抗感染药物咨询委员会的建议批准了zyvox的上市申请。

 

 

【药品名称】

利奈唑胺片

斯沃Zyvo

【药品介绍】
人工合成的唑烷酮类抗生素,2000年获得美国FDA批准,用于治疗革兰阳性(G+)球菌引起的感染,包括由MRSA引起的疑似或确诊院内获得性肺炎(HAP)、社区获得性肺炎(CAP)、复杂性皮肤或皮肤软组织感染(SSTI)以及耐万古霉素肠球菌(VRE)感染。

利奈唑胺为细菌蛋白质合成抑制剂，作用于细菌50S核糖体亚单位，并且最接近作用部位。与其它药物不同，利奈唑胺不影响肽基转移酶活性，只是作用于翻译系统的起始阶段，抑制mRNA与核糖体连接，阻止70S起始复合物的形成，从而抑制了细菌蛋白质的合成。利奈唑胺的作用部位和方式独特，因此在具有本质性或获得性耐药特征的阳性细菌中，都不易与其它抑制蛋白合成的抗菌药发生交叉耐药，在体外也不易诱导细菌耐药性的产生。研究表明，通常导致阳性细菌对作用于50S核糖体亚单位的抗菌药物产生耐药性的基因对利奈唑胺均无影响，包括存在修饰酶、主动外流机制以及细菌靶位修饰和保护作用。

利奈唑胺对甲氧西林敏感或耐药葡萄球菌、万古霉素敏感或耐药肠球菌、青霉素敏感或耐药肺炎链球菌均显示了良好的抗菌作用，对厌氧菌亦具抗菌活性。有关利奈唑胺敏感性的分析表明，利奈唑胺对从皮肤、血液和肺中分离到的3382 株细菌中的甲氧西林敏感或耐药性金黄色葡萄球菌、表皮葡萄球菌、酿脓链球菌（Streptococcuspyogenes，一种A组茁溶血性链球菌）、肺炎链球菌、无乳链球菌和肠球菌属等均具有良好活性，MIC50范围为0.5～4毫克/升；对卡它莫拉菌和流感嗜血杆菌具有中度活性，MIC50为4～16 毫克/升。

【适应症】
用于治疗由特定微生物敏感株引起的下列感染： 　　
1、耐万古霉素的屎肠球菌引起的感染，包括并发的菌血症； 　　
2、院内获得性肺炎(hap)，致病菌为金黄色葡萄球菌(甲氧西林敏感或耐甲氧西林的菌珠)或肺炎链球菌(包括多药耐药的菌株[mdrsp])。如果已证实或怀疑存在革兰氏阴性致病菌感染，临床上需要联合应用抗革兰氏阴性菌的药物； 　　
3、复杂性皮肤或皮肤软组织感染(ssti)，包括未并发骨髓炎的糖尿病足部感染，由金黄色葡萄球菌(甲氧西林敏感或耐甲氧西林的菌珠)、化脓链球菌或无孔链球菌引起。尚无利奈唑胺用于治疗褥疮的研究。 　　
只有当微生物实验检查显示敏感性革兰氏阳性菌感染时才应该使用利奈唑胺治疗复杂性皮肤或皮肤软组织感染。如果已证实或怀疑同时存在革兰氏阴性致病菌感染，在没有其他有效治疗措施时才使用利奈唑胺，还必须联合应用抗革兰氏阴性菌的药物； 　　
4、非复杂性皮肤或皮肤软组织感染，由金黄色葡萄球菌(仅为甲氧西林敏感的菌珠)所致； 　　
5、社区获得性肺炎(cap)及伴发的菌血症，由肺炎链球菌(包括对多药耐药的菌株[mdrsp])，或由金黄色葡萄球菌(仅为甲氧西林敏感的菌珠)所致。

【用法用量】
治疗由革兰氏阳性致病敏感菌引起的下列感染时的推荐剂量： 　　
治疗复杂性皮肤或皮肤软组织感染、社区获得性肺炎及伴发的菌血症、院内获得性肺炎，成人和青少年(12岁及12岁以上，下同)每12小时静注或口服(片剂或口服混悬剂)600mg，儿童患者(刚出生至11岁，下同)每8小时静注或口服(片剂或口服混悬剂)10mg/kg。连续治疗10-14天。 　　
治疗万古霉素耐药的屎肠球菌感染及伴发的菌血症，成人和青少年每12小时静注或口服(片剂或口服混悬剂)600mg，儿童患者每8小时静注或口服(片剂或口服混悬剂)10mg/kg。连续治疗14-28天。 　　
治疗单纯性皮肤或皮肤软组织感染，成人每12小时口服400mg，青少年每12小时口服600mg。儿童患者＜5岁，每8小时按10mg/kg口服；5-11岁，每12小时按10mg/kg口服。连续治疗10-14天。 　　
甲氧西林耐药金黄色葡萄球菌(mrsa)感染的成人患者，用利奈唑胺600mg每12小时一次进行治疗。 　　
所有的新生儿童患者应按10mg/kg，每8小时一次，连续使用7天的方案给药。大多数出生7天以内的早产(＜34孕周)患儿较足月儿和其他婴儿对利奈唑胺的系统清除率低，且全身药物暴露量(auc)值大，因此初始剂量应为10mg/kg每12小时给药，当临床效果不佳时，应考虑按剂量为10mg/kg每8 小时给药 　　
当从静脉给药转换成口服给药时无需调整剂量。对起始治疗时应用利奈唑胺注射液的患者，医生可根据临床状况，予以利奈唑胺片剂或口服混悬液继续治疗。无论是静脉给药还是口服给药，如果没有完成整个治疗过程，可能会降低治疗效果，并且增加细菌耐药发生的可能。 　　
利奈唑胺静脉注射液应在30至120分钟内静脉输注。不能将此静脉输液袋串联在其他静脉给药通路中。不可在此溶液中加入其他药物。如果利奈唑胺静脉注射需与其它药物合并应用，应根据每种药物的推荐剂量和给药途径分别应用。利奈唑胺静脉注射液与下列药物通过y型接口联合给药时，可导致物理性质不配伍：二性霉素 b、盐酸氯丙嗪、地西泮、喷他眯异硫代硫酸盐、红霉素乳糖酸脂、苯妥英钠和甲氯苄啶-磺胺甲基异恶唑。此外，利奈唑胺静脉注射液与头孢曲松钠合用可致二者的化学性质不配伍。 　　
如果同一静脉通路用于几个药物依次给药，在应用利奈唑胺静脉注射液前及使用后，须输注与利奈唑胺静脉注射液和其它药物可配伍的溶液。能与利奈唑胺静脉注射液配伍的静脉注射液有：5%葡萄糖注射液、0.9%氯化钠注射液、乳酸林格氏液。 　　
利奈唑胺静脉注射液为无色至淡褐色的澄明液体，随着时间延长可加深，但不负面影响药物的含量(在有效期内)。应在静脉给药前目测是否有微粒物质，用力挤压输液袋以检查细微的渗漏。若发现问题则不能使用。

 

【不良反应】
利奈唑胺最常见的不良事件为腹泻、头痛和恶心。其他不良事件有呕吐、失眠、便秘、皮疹、头晕、发热、口腔念珠菌病、阴道念珠菌病、真菌感染、局部腹痛、消化不良、味觉改变、舌变色、瘙痒。 　　
利奈唑胺上市后见于报道的不良反应有骨髓抑制(包括贫血、白细胞减少、各类血细胞减少和血小板减少)、周围神经病和视神经病(有的进展至失明)、乳酸性酸中毒。这些不良反应主要出现在用药时间过长(超过28天)的患者中。利奈唑胺合用5-羟色胺类药物(包括抗抑郁药物如：选择性5-羟色胺再摄取抑制剂 [ssris])的患者中，有5-羟色胺综合征的报道。 　　
禁忌：本品禁用于已知对利奈唑胺或本品其他成份过敏的患者。(利奈唑胺注射液中的非活性成分有：枸橼酸钠、枸橼酸、葡萄糖。利奈唑胺口服干混悬剂中含苯丙氨酸)

 

【注意事项】
1、为减少细菌对药物耐药的发生和保持利奈唑胺和其他抗菌药物的疗效，利奈唑胺应仅用于确诊或高度怀疑敏感菌所致感染的治疗或预防。当获悉细菌培养和药物敏感性结果，应当考虑选择或调整抗菌治疗。如缺乏这些资料，当地的流行病学和药物敏感性状况可能有利于经验性治疗的选择。利奈唑胺的适应症不包括革兰氏阴性菌的治疗，如果怀疑或确认感染了革兰氏阴性菌，应立即进行针对性的治疗。 　　
2、在抗菌药物的分级管理中，利奈唑胺被列入特殊管理。在没有确诊或高度怀疑细菌感染的证据或没有预防指征时，处方利奈唑胺可能不会给患者带来益处，且有增加耐药细菌产生的风险。 　　
3、由于在治疗导管相关性感染的严重病例的研究试验中，利奈唑胺组的死亡率与对照组相当或更高，因此利奈唑胺没有被批准用于导管相关性血流感染、导管接触部位感染。 　　
4、对使用利奈唑胺的患者应每周进行全血细胞计数的检查，尤其是用药超过两周，或以前有过骨髓抑制病史，或合并使用能诱导发生骨髓抑制的其他药物，或患慢性感染既往或目前合并接受其他抗菌药物治疗的患者。对发生骨髓抑制或骨髓抑制发生恶化的患者应考虑停用利奈唑胺。在已知病例中，停用利奈唑胺后血象指标可以上升并恢复到治疗前的水平。 　　
5、几乎所有抗菌药物包括利奈唑胺，均有伪膜性结肠炎的报道，严重程度可为轻度至威胁生命。因此对于使用任何抗菌药物后出现腹泻的病人，诊断时要考虑是否是伪膜性结肠炎。当确诊为伪膜性结肠炎时，轻度的通常停药即可痊愈。中度及重度患者，应考虑给予补液，补充电解质和蛋白质，并给与临床上对难辨梭菌有效的抗菌药物治疗。 　　
6、如患者出现视力损害的症状时，如视敏度改变、色觉改变、视力模糊或视野缺损，应及时进行眼科检查。对于所有长期(大于等于3个月)使用利奈唑胺的患者及报告有新视觉症状的患者，不论其接受利奈唑胺治疗时间的长短，应当进行视觉功能监测。多数视神经病变可于停药后缓解，但周围神经病变并非如此。如发生周围神经病和视神经病，应进行用药与潜在风险评价，以判断是否继续用药。 　　
7、使用利奈唑胺过程中，有乳酸性酸中毒的报道。患者在接受利奈唑胺治疗时如发生反复恶心或呕吐、有不明原因的酸中毒或低碳酸血症，需要立即进行临床检查。 　　
患者应被告知如下信息： 　　
1、利奈唑胺可与食物共用或分开服用。 　　
2、如果患者有高血压病史，应告知医师。 　　
3、当使用利奈唑胺时，应避免食用大量酪胺含量高的食物和饮料。每餐摄入的酪胺量应低于100mg。酪胺含量高的食物包括那些通过储存、发酵、盐渍和烟熏来矫味而引起的蛋白质变性，例如陈年乳酪(每盎司含0-15mg酪胺)、发酵过或风干的肉类(每盎司含0.1-8mg酪胺)、泡菜(每盎司含1mg酪胺)、酱油(每一茶匙含5mg酪胺)、生啤(每3盎司含1mg酪胺)、红酒(每8盎司含0-6mg酪胺)。如果长期贮存或不适当的冷藏，任何一种富含蛋白质的食物其酪胺含量均会增加。 　　
4、如果患者正在服用含盐酸伪麻黄碱或盐酸苯丙醇胺的药物，如抗感冒药物和缓解充血的药物，应告知医师。 　　
5、如果患者正在使用5-羟色胺再摄取抑制剂或其他抗抑郁剂时，应告知医师。 　　
6、苯酮尿：每5ml规格为100mg/5ml的利奈唑胺口服干混悬剂中含有20mg苯丙氨酸。其他利奈唑胺制剂不含苯丙氨酸。应与你的医师或药师联络。 　　
7、出现视觉改变时，应当告知医师。 　　
应当告知患者：抗菌药物包括利奈唑胺应仅用于细菌感染，不应当用于治疗病毒感染(如：感冒)。当用利奈唑胺治疗细菌感染时，在治疗过程的早期虽然患者通常会感觉好转，仍应当按照医嘱准确服药。给药的疏漏或没有完成整个治疗过程，可能会降低治疗效果，并且增加细菌耐药发生的可能以及将来不能被利奈唑胺或其他抗菌药物治疗的可能。

 

【孕妇及哺乳期妇女用药】
利奈唑胺及其代谢产物可分泌至哺乳期大鼠的乳汁中。乳汁中的药物浓度与母体的血浆药物浓度相似。利奈唑胺是否分泌至人类的乳汁中尚不明确。由于许多药物都能随人类的乳汁分泌，因此利奈唑胺应慎用于哺乳期妇女。 　　
尚未在妊娠妇女中进行充分的、有对照的临床研究。只有潜在的益处超过对胎儿的潜在风险时，才建议妊娠妇女使用。

 

【儿童用药】
利奈唑胺用于治疗儿童患者下列感染时的安全性和有效性已得到临床研究证实：院内感染的肺炎、复杂性皮肤或皮肤软组织感染、社区获得性肺炎、对万古霉素耐药的屎肠球菌感染以及由对甲氧西林耐药的金黄色葡萄球菌和化脓性链球菌引起的非复杂性皮肤或皮肤软组织感染。 　　
在经脑室腹膜分流术的儿童患者中得到的药代动力学资料显示，给予单剂或多剂利奈唑胺后，脑脊液中的药物浓度差异较大，且未能持续获得或维持脑脊液的治疗浓度。因此，不推荐利奈唑胺经验性用于儿童患者的中枢神经系统感染。 　　
在有限的临床经验中，6例儿童患者中的5例，其感染的革兰氏阳性病原体的最低抑菌浓度为4µg/ml，经利奈唑胺治疗后临床痊愈。然而，与成人相比，儿童患者的利奈唑胺清除率和全身药物暴露量的变化范围更宽。当儿童患者的临床疗效未达到最佳时，尤其是病原体的最低抑菌浓度为4µg/ml，在作疗效评估时应考虑其较低的全身暴露药量、感染部位及其严重程度和以及潜在的病情。 　　
在儿童患者中，利奈唑胺的最大血药浓度(cmax)和分布体积(vss) 与年龄无关，清除率与年龄相关。排除出生不到7天的早产儿，年龄最小的儿童组(出生7天至11岁)与成人相比，清除率最快，从而导致了单剂量给药后较低的全身药物暴露量(auc)和较短的半衰期。随着儿童患者年龄的增加，利奈唑胺的清除率逐渐降低，青春期的儿童患者的清除率已与成年患者的相似。与成人相比，在所有不同年龄层的儿童患者中观察到清除率与auc存在更大的个体差异。 　　
新生儿至11岁的儿童患者每8小时给药一次的日平均auc值与青少年和成人患者每12小时给药一次的日平均auc值相似。因而11岁及小于11岁儿童患者的给药剂量应为10mg/kg，每8小时一次。12岁及其以上的儿童患者给药剂量为600mg每12小时一次。 　　
与足月的新生儿和较大的新生儿相比，大多数出生7天以内的早产儿(＜34孕周)对利奈唑胺的系统清除率较低，且auc值较高。所以，早产儿的治疗应从 10mg/kg，每12小时一次的初始剂量开始。对未取得最佳临床疗效的新生儿可考虑采用10mg/kg，每8小时一次的治疗方案。

 

【老年人用药】
在ⅲ期对照研究中，未见65岁以上患者与年轻患者之间有安全性和有效性的差异。

【药物相互作用】
通过细胞色素酶p450代谢的药物：在大鼠中，利奈唑胺不是细胞色素酶p450(cyp)的诱导剂。利奈唑胺既不能由人细胞色素酶p450代谢，也不能抑制有临床意义的人类细胞色素同工酶(1a2,2c9；2c19,2d6,2e1和3a4)的活性。所以，预计利奈唑胺不会与由细胞色素酶p450诱导代谢的酶产生相互作用。与利奈唑胺联合用药，不会改变主要由cyp2c9进行代谢的(s)-华法林的药代动力学性质。如华法林、苯妥因等药物，作为cyp2c9 的底物，可与利奈唑胺联合用药而无须改变给药方案。 　　
氨曲南：当二者合用时，利奈唑胺与氨曲南的药代动力学特性均未发生改变。 　　
庆大霉素：当二者合用时，利奈唑胺与庆大霉素的药代动力学特性均未发生改变。 　　
单胺氧化酶抑制作用：利奈唑胺为可逆的、非选择性的单胺氧化酶抑制剂。所以利奈唑胺与肾上腺素能(拟交感神经)或5-羟色胺类制剂有潜在的相互作用。 　　
拟交感神经药物：当健康受试者同时接受利奈唑胺及超过100mg的酪胺时，可见明显的加压反应。所以，使用利奈唑胺的患者应避免食用酪胺含量高的食物和饮料(见“注意事项”)。 　　
对血压正常的健康志愿者给予利奈唑胺，可观察到利奈唑胺能可逆性地增加伪麻黄碱(pse)、盐酸苯丙醇胺(ppa)的加压作用。利奈唑胺与ppa或rse联用均能使血压上升。在ppa或rse第二次给药后的2-3小时，观察到最高的血压值；在达峰值后的2-3小时，血压又回复到了基础水平。ppa的研究结果与rse的研究结果相似。当利奈唑胺与ppa或rse联用时，高于基础收缩压的平均最大增加值分别为32mmhg(范围：20-52mmhg)和 38mmhg(范围：18-79mmhg)。未对高血压患者进行类似的研究。 　　
对5-羟色胺类药物的作用：对健康志愿者进行了利奈唑胺与右美沙芬潜在药物相互作用的研究。给与志愿者右美沙芬(二个剂量，每次20mg，间隔4小时)，同时给予或不给予利奈唑胺。在接受右美沙芬和利奈唑胺的血压正常的志愿者中未观察到5-羟色胺综合征的作用(意识模糊、极度兴奋、不安、震颤、潮红、发汗以及体温升高)。但是，在临床使用中有5-羟色胺综合征的报道 (见“不良反应”)。

 

【药物过量】
用药过量时，建议应用支持疗法以维持肾小球的滤过，血液透析能加速利奈唑胺的清除。在i期临床研究中，给予利奈唑胺3小时后，通过3小时的血液透析，30%剂量的药物被清除。尚无腹膜透析或血液滤过清除利奈唑胺的资料。当分别给予3000mg/kg/天和 2000mg/kg/天的利奈唑胺时，动物急性中毒的临床症状为大鼠活动力下降和运动失调，狗出现呕吐和颤抖。

 

【药理毒理】
利奈唑胺是细菌蛋白质合成抑制剂，与细菌50s亚基上核糖体rna的23s位点结合，从而阻止形成70s始动复合物，前者为细菌转译过程中非常重要的组成部分。由于利奈唑胺不影响肽基转移酶活性，只是作用于翻译系统的起始阶段，抑制mrna与核糖体连接，从而抑制了细菌蛋白质的合成。因此在具有本质性或获得性耐药特征的阳性细菌中，都不易与其它抑制蛋白合成的抗菌药发生交叉耐药，在体外也不易诱导细菌耐药性的产生。研究表明，通常导致阳性细菌对作用于50s核糖体亚单位的抗菌药物产生耐药性的基因对利奈唑胺无影响，包括存在修饰酶、主动外流机制以及细菌靶位修饰和保护作用。时间—杀菌曲线研究结果表明利奈唑胺为肠球菌和葡萄球菌的抑菌剂，为大多数链球菌菌株的杀菌剂。 　
体外试验和临床使用结果均表明利奈唑胺对以下微生物的大多数菌株具有抗菌活性：需氧的和兼性的革兰氏阳性致病菌，屎肠球菌(仅指耐万古霉素的菌珠)，金黄色葡萄球菌(包括耐甲氧西林的菌珠)，无乳链球菌、肺炎链球菌(包括对多药耐药的菌株 [mdrsp])，化脓性链球菌。 　　
下列菌株中至少90%体外最低抑菌浓度(mic)低于或等于利奈唑胺的敏感范围：需氧的和兼性的革兰氏阳性致病菌、粪肠球菌(包括耐万古霉素的菌珠)、屎肠球菌(万古霉素敏感的菌珠)、表皮葡萄球菌(包括耐甲氧西林的菌珠)、嗜血葡萄球菌属、草绿色链球菌属、需氧的和兼性的革兰氏阴性致病菌、多杀巴斯德菌。该数据仅为体外研究资料，其临床意义尚不明确，尚未通过充分的及严格对照的临床研究证实利奈唑胺临床上用于治疗由这些微生物引起的感染的安全性和有效性。 　　
毒理研究在未成年和成年的大鼠和狗中，利奈唑胺的毒性靶器官相似，表现为骨髓细胞减少血细胞生成减少、脾脏和肝脏的髓外血细胞生成减少，以及外周血红细胞、白细胞和血小板水平下降。胸腺、淋巴结和脾脏出现淋巴组织缺失。对骨髓抑制的作用与时间和剂量相关。上述作用剂量与一些人类受试者中观察到的作用剂量相当。对血象和淋巴系统的作用虽然在某些研究的恢复期内未能完全恢复，但是是可逆的。 　　
遗传毒性：利奈唑胺对基因突变试验(ames细菌回复突变试验和中国仓鼠卵巢细胞染色体畸变试验)、体外非常规dna合成(uds)试验、体外人淋巴细胞的染色体缺陷分析和小鼠的体内微核试验结果均为阴性。 　　
生殖毒性：利奈唑胺不影响成年雌性大鼠的生殖力或生育行为。当对成年雄性大鼠以≧50mg/kg/天的剂量给药时(根据auc推算，该剂量相当于或大于人类的给药剂量)，能可逆性地降低雄性大鼠的生殖力和生育行为。对生殖功能的可逆作用是通过改变精子的生成而介导的。受影响的精细胞包含形态和定向异常的线粒体并且是没有活力的。观察到的附睾中上皮细胞的肥大和增生与生殖力的降低有关。狗中未见相似的附睾变化。 　　
在未成年雄性大鼠性发育的绝大部分时期给予利奈唑胺(50mg/kg/天,从出生的第7-36天；100mg/kg/天，从出生的37-55天，按平均的auc推算，相当于人类3个月至 11岁的儿童给药剂量的1.7倍)，发现可轻度降低性成熟雄性大鼠的生殖力。在对受孕和新生儿早期(相当于受孕第6天至产后第5天)、新生儿期(产后5至 21天)、或未成年期(产后22至35天)的药物暴露观察中，未观察到较短治疗期对生育力的影响。大鼠在出生22天至35天给药，观察到可逆的精子活动力降低和精子形态的改变。 　　
小鼠给予450mg/kg/天(以auc计算，相当于人类给药剂量的6.5倍剂量给药)，见着床胚胎的死亡率，包括总胎仔数减少，胎仔体重减少，增加肋软骨融合的发生率。大鼠给予15和50mg/kg/天 (以auc计算，相当于人类给药剂量的0.22倍至约等同于人用剂量)时，可观察到对胎仔轻微的毒性。毒性作用包括：减少胎仔的重量，减少胸骨的骨化，后者常与胎仔体重减少相关。在50mg/kg/d组，还可见体重减少的轻微母体毒性。 　　
在妊娠至哺乳期间给予雌性大鼠以50mg/kg/天(以auc计算，相当于人用剂量)，产后1-4天存活的幼仔数减少。存活的雌性或雄性幼仔至性成熟时交配，可见未着床胚胎数的增加。

 

【药代动力学】
吸收：口服给药后，利奈唑胺吸收快速而完全。给药后约1-2小时达到血浆峰浓度，绝对生物利用度约为100%。所以，利奈唑胺口服或静脉给药无需调整剂量。 　　
    利奈唑胺的给药无须考虑进食的时间。当利奈唑胺与高脂食物同时服用时，达峰时间从1.5小时延迟到2.2小时，峰浓度约下降17%。然而总的暴露量指标auc0→∞的值在两种情况下是相似的。 　　
分布：为31%且有浓度依赖性。在健康志愿者中，稳态时利奈唑胺的分布容积平均为40-50l。 　　
在研究利奈唑胺多次给药的i期临床研究中，对有限例数健康受试者的多种体液中的利奈唑胺浓度进行了测定。利奈唑胺在唾液与血浆中的比率为1.2:1；在汗液与血浆中的比率为0.55:1。 　　
代谢：利奈唑胺的主要代谢为吗啉环的氧化，它可产生两个无活性的开环羧酸代谢产物：氨基乙氧基乙酸代谢物(a)和羟乙基氨基乙酸代谢物(b)。
在体外，代谢产物b通过非酶介导的化学氧化机制形成。在大鼠中，利奈唑胺不是细胞色素酶p450(cyp)的诱导剂，并且在体外试验中已证明利奈唑胺不通过人细胞色素酶p450代谢，也不抑制有临床意义的人类细胞色素同工酶(1a2,2c9；2c19,2d6,2e1和3a4)的活性。 　　
排泄：非肾脏清除率约占利奈唑胺总清除率的65%。稳态时，约有30%药物以利奈唑胺的形式、40%以代谢产物b的形式、10%以代谢产物a的形式随尿排泄。利奈唑胺的肾脏清除率低(平均为40ml/分钟)，提示有肾小管网的重吸收。事实上，粪便中无利奈唑胺，大约有6%和3%的药物分别以代谢产物b和a的形式出现在粪便中。 　　
随着利奈唑胺剂量的增加，可观察到利奈唑胺轻微的非线性清除，表现为在高浓度时利奈唑胺的肾清除率和非肾清除率降低。然而，清除率的变化很小，不足以影响利奈唑胺的表观消除半衰期。 　　
特殊人群
老年人：在老年患者(≧65岁)中，利奈唑胺的药代动力学性质改变不甚明显。所以，无需对老年患者作剂量调整。 　　
儿童：在刚出生至17岁的儿童患者(含早产儿及足月出生的新生儿)、12-17岁的健康青少年以及出生后一周至12岁的儿童患者中进行的利奈唑胺单剂量静脉给药的药代动力学研究表明：利奈唑胺的cmax和分布容积(vss)在各年龄层的儿童患者中相似，与儿童患者的年龄无关。然而，利奈唑胺的清除率在各年龄层的儿童患者中有所不同。剔除出生不到一周的早产儿后，年龄最小的儿童组(即出生一周后至11岁)，其清除速率最快，导致与成人相比单剂量给药后全身药物暴露量(auc)降低和半衰期缩短。随着儿童患者年龄的增加，利奈唑胺的清除率逐渐降低。青少年患者的清除率与成年人的相似。与成年人相比，清除率与全身药物暴露量在所有不同年龄层的儿童患者中存在更大的个体差异。 　　
新生儿至11岁的儿童患者每8小时给药一次的日平均auc值与青少年和成年患者每12小时给药一次的日平均auc值相似。因而，11岁及小于11岁儿童患者的给药剂量应为10mg/kg，每8小时一次。12岁及其以上的儿童患者给药剂量为600mg每12小时一次。出生7天以内的早产儿(＜34孕周)患者对利奈唑胺的系统清除率较低，且auc值较高。所以，给药应从 10mg/kg，每12小时一次的初始剂量开始，疗效不佳时可每8小时给药一次。 　　
性别：女性与男性相比，利奈唑胺分布容积较小。女性的血浆浓度高于男性，部分由体重差异引起。口服给药600mg后，女性的平均清除率约较男性低38%。然而，平均表观清除速率常数和半衰期未见明显的性别差异。因此，女性的药物暴露量不会明显地超过已知可耐受的水平。故无须针对性别进行剂量调整。 　　
肾功能不全：不同程度的肾功能不全患者，其原形药物利奈唑胺的药代动力学性质不发生改变。肾功能不全患者，两种主要代谢产物可能产生蓄积，且蓄积随肾功能不全的严重程度增加而增加。尚未在严重肾功能不全患者中对上述两种代谢产物蓄积的临床意义进行研究。无论肾功能如何，患者都能获得相似的利奈唑胺血浆药物浓度，因此无须对肾功能不全的患者调整剂量。由于缺乏对两种主要代谢产物在体内蓄积的临床意义的认识，对肾功能不全患者应权衡使用利奈唑胺与其代谢物蓄积潜在风险间的利弊。利奈唑胺及其两种代谢产物都可通过透析清除。尚没有腹膜透析影响利奈唑胺药代动力学特性的资料。利奈唑胺给药后3小时开始透析，在大约3小时的透析期内约30%的药物剂量可清除。因此，利奈唑胺应在血透结束后给药。 　　
肝功能不全：对7位轻至中度肝功能不全患者(child-pugh分级a或b)的研究表明，利奈唑胺的药代动力学性质未见改变。根据现有的资料，无须对轻至中度肝功能不全患者调整剂量。尚未对肝功能严重不全的患者评价利奈唑胺的药代动力学特征。

【贮藏】
避光，密封，在15-30℃条件下保存。避免冷冻。

 

rug Description

 

 

ZYVOX®
(linezolid) Injection, Tablets and Oral Suspension

DESCRIPTION

ZYVOX I.V. Injection, ZYVOX Tablets, and ZYVOX for Oral Suspension contain linezolid, which is a synthetic antibacterial agent of the oxazolidinone class. The chemical name for linezolid is (S)-N-[[3-[3-Fluoro-4-(4morpholinyl)phenyl]-2-oxo-5-oxazolidinyl] methyl]-acetamide.

The empirical formula is C16H20FN3O4. Its molecular weight is 337.35, and its chemical structure is represented below:

ZYVOX I.V. Injection is supplied as a ready-to-use sterile isotonic solution for intravenous infusion. Each mL contains 2 mg of linezolid. Inactive ingredients are sodium citrate, citric acid, and dextrosein an aqueous vehicle for intravenous administration. The sodium (Na+) content is 0.38 mg/mL (5 mEq/300-mL bag and 1.7 mEq/100-mL bag).

ZYVOX Tablet for oral administration contains 600 mg linezolid as a film-coated compressed tablet. Inactive ingredients are corn starch, microcrystalline cellulose, hydroxypropylcellulose, sodium starch glycolate, magnesium stearate, hypromellose, polyethylene glycol, titanium dioxide, and carnauba wax. The sodium (Na+) content is 2.92 mg per 600-mg tablet (0.1 mEq/tablet).

ZYVOX for Oral Suspension is supplied as an orange-flavored granule/powder for constitution into a suspension for oral administration. Following constitution, each 5 mL contains 100 mg of linezolid. Inactive ingredients are sucrose, citric acid, sodium citrate, microcrystalline cellulose and carboxymethylcellulose sodium, aspartame, xanthan gum, mannitol, sodium benzoate, colloidal silicon dioxide, sodium chloride, and flavors [see PATIENT INFORMATION]. The sodium (Na+) content is 8.52 mg/5 mL (0.4 mEq/5 mL).

Indications

INDICATIONS

ZYVOX is indicated for the treatment of infections caused by susceptible strains of the designated microorganisms in the specific conditions listed below. ZYVOX is not indicated for the treatment of Gram-negative infections. It is critical that specific Gram-negative therapy be initiated immediately if a concomitant Gram-negative pathogen is documented or suspected [see WARNINGS AND PRECAUTIONS].

Pneumonia

Nosocomial pneumonia caused by Staphylococcus aureus (methicillin-susceptible and -resistant isolates) or Streptococcus pneumoniae [see Clinical Studies].

Community-acquired pneumonia caused by Streptococcus pneumoniae, including cases with concurrent bacteremia, or Staphylococcus aureus (methicillin-susceptible isolates only) [see Clinical Studies].

Skin and Skin Structure Infections

Complicated skin and skin structure infections, including diabetic foot infections, without concomitant osteomyelitis, caused by Staphylococcus aureus (methicillin-susceptible and -resistant isolates), Streptococcus pyogenes, or Streptococcus agalactiae. ZYVOX has not been studied in the treatment of decubitus ulcers [see Clinical Studies].

Uncomplicated skin and skin structure infections caused by Staphylococcus aureus (methicillin-susceptible isolates only) or Streptococcus pyogenes [see Clinical Studies].

Vancomycin-Resistant Enterococcus Faecium Infections

Vancomycin-resistant Enterococcus faecium infections, including cases with concurrent bacteremia [see Clinical Studies].

Usage

To reduce the development of drug-resistant bacteria and maintain the effectiveness of ZYVOX and other antibacterial drugs, ZYVOX should be used only to treat infections that are proven or strongly suspected to be caused by susceptible bacteria. When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy.

The safety and efficacy of ZYVOX formulations given for longer than 28 days have not been evaluated in controlled clinical trials.

Dosage

DOSAGE AND ADMINISTRATION

General Dosage And Administration

The recommended dosage for ZYVOX formulations for the treatment of infections is described in Table 1.

Table 1. Dosage Guidelines for ZYVOX

No dose adjustment is necessary when switching from intravenous to oral administration.

Intravenous Administration

ZYVOX I.V. Injection is supplied in single-use, ready-to-use infusion bags. Parenteral drug products should be inspected visually for particulate matter prior to administration. Check for minute leaks by firmly squeezing the bag. If leaks are detected, discard the solution, as sterility may be impaired. Keep the infusion bags in the overwrap until ready to use. Each overwrap contains a peel-off label. Apply the peel-off label to the infusion bag for barcode scanning before use. Store at room temperature. Protect from freezing. ZYVOX I.V. Injection may exhibit a yellow color that can intensify over time without adversely affecting potency.

ZYVOX I.V. Injection should be administered by intravenous infusion over a period of 30 to 120 minutes. Do not use this intravenous infusion bag in series connections. Additives should not be introduced into this solution. If ZYVOX I.V. Injection is to be given concomitantly with another drug, each drug should be given separately in accordance with the recommended dosage and route of administration for each product.

If the same intravenous line is used for sequential infusion of several drugs, the line should be flushed before and after infusion of ZYVOX I.V. Injection with an infusion solution compatible with ZYVOX I.V. Injection and with any other drug(s) administered via this common line.

Compatibilities

Compatible intravenous solutions include 0.9% Sodium Chloride Injection, USP, 5% DextroseInjection, USP, and Lactated Ringer’s Injection, USP.

Incompatibilities

Physical incompatibilities resulted when ZYVOX I.V. Injection was combined with the following drugs during simulated Y-site administration: amphotericin B, chlorpromazine HCl, diazepam, pentamidine isothionate, erythromycin lactobionate, phenytoin sodium, and trimethoprim-sulfamethoxazole. Additionally, chemical incompatibility resulted when ZYVOX I.V. Injection was combined with ceftriaxone sodium.

Constitution Of Oral Suspension

ZYVOX for Oral Suspension is supplied as a powder/granule for constitution. Gently tap bottle to loosen powder. Add a total of 123 mL distilled water in two portions. After adding the first half, shake vigorously to wet all of the powder. Then add the second half of the water and shake vigorously to obtain a uniform suspension. After constitution, each 5 mL of the suspension contains 100 mg of linezolid. Before using, gently mix by inverting the bottle 3 to 5 times. Do not shake. Store constituted suspension at room temperature. Use within 21 days after constitution.

HOW SUPPLIED

Dosage Forms And Strengths

ZYVOX I.V. Injection: 100-mL (200 mg linezolid) and 300-mL (600 mg linezolid) single-use, ready-to-use flexible plastic infusion bags in a foil laminate overwrap. The infusion bags and ports are latex-free.

ZYVOX 600 mg Tablet

white, capsule-shaped, film-coated tablet printed with “ZYVOX 600 mg”
white, capsule-shaped, film-coated tablet debossed with “ZYV” on one side and “600” on the other

ZYVOX for Oral Suspension: dry, white to off-white, orange-flavored granule/powder. When constituted as directed, each bottle will contain 150 mL of a suspension providing the equivalent of 100 mg of linezolid per each 5 mL.

Storage And Handling

Injection

ZYVOX I.V. Injection is available in single-use, ready-to-use flexible plastic infusion bags in a foil laminate overwrap. The infusion bags and ports are latex-free. The infusion bags are available in the following package sizes:

100 mL bag (200 mg linezolid) - NDC 0009-5137-01
100 mL bag (200 mg linezolid) x 10 - NDC 0009-5137-04
300 mL bag (600 mg linezolid) - NDC 0009-5140-01
300 mL bag (600 mg linezolid) x 10 - NDC 0009-5140-04

Tablets

ZYVOX Tablets are available as follows:

600 mg (white, capsule-shaped, film-coated tablets printed with “ZYVOX 600 mg”)

100 tablets in HDPE bottle - NDC 0009-5135-01
20 tablets in HDPE bottle - NDC 0009-5135-02
Unit dose packages of 30 tablets - NDC 0009-5135-03

600 mg (white, capsule-shaped, film-coated tablets debossed with “ZYV” on one side and “600” on the other)

20 tablets in HDPE bottle - NDC 0009-5138-02
Unit dose packages of 30 tablets - NDC 0009-5138-03

Oral Suspension

ZYVOX for Oral Suspension is available as a dry, white to off-white, orange-flavored granule/powder. When constituted as directed, each bottle will contain 150 mL of a suspension providing the equivalent of 100 mg of linezolid per each 5 mL. ZYVOX for Oral Suspension is supplied as follows:

100 mg/5 mL in 240-mL glass bottles - NDC 0009-5136-01

Storage And Handling

Store at 25°C (77°F). Protect from light. Keep bottles tightly closed to protect from moisture. It is recommended that the infusion bags be kept in the overwrap until ready to use. Each overwrap contains a peel-off label. Apply the peel-off label to the infusion bag for barcode scanning before use. Protect infusion bags from freezing.

Distributed by: Pfizer pharmacia&upjohn Co, division of Pfizer Inc, NY 10017. Revised: July 2017

Side Effects & Drug Interactions

SIDE EFFECTS

Clinical Trials Experience

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.

Adults

The safety of ZYVOX formulations was evaluated in 2046 adult patients enrolled in seven Phase 3 comparator-controlled clinical trials, who were treated for up to 28 days.

Of the patients treated for uncomplicated skin and skin structure infections (uSSSIs), 25.4% of ZYVOX-treated and 19.6% of comparator-treated patients experienced at least one drug-related adverse event. For all other indications, 20.4% of ZYVOX -treated and 14.3% of comparator-treated patients experienced at least one drug-related adverse event.

Table 2 shows the incidence of all-causality, treatment-emergent adverse reactions reported in at least 1% of adult patients in these trials by dose of ZYVOX.

Table 2. Incidence (%) of Treatment–Emergent Adverse Reactions Occurring in >1% of Adult Patients Treated with ZYVOX in Comparator-Controlled Clinical Trials

Of the patients treated for uSSSIs, 3.5% of ZYVOX-treated and 2.4% of comparator-treated patients discontinued treatment due to drug-related adverse events. For all other indications, discontinuations due to drug-related adverse events occurred in 2.1% of ZYVOX-treated and 1.7% of comparator-treated patients. The most common reported drug-related adverse events leading to discontinuation of treatment were nausea, headache, diarrhea, and vomiting.

Pediatric Patients

The safety of ZYVOX formulations was evaluated in 215 pediatric patients ranging in age from birth through 11 years, and in 248 pediatric patients aged 5 through 17 years (146 of these 248 were age 5 through 11 and 102 were age 12 to 17). These patients were enrolled in two Phase 3 comparator-controlled clinical trials and were treated for up to 28 days. In the study of hospitalized pediatric patients (birth through 11 years) with Gram-positive infections, who were randomized 2 to 1 (linezolid: vancomycin), mortality was 6.0% (13/215) in the linezolid arm and 3.0% (3/101) in the vancomycin arm. However, given the severe underlying illness in the patient population, no causality could be established.

Of the pediatric patients treated for uSSSIs, 19.2% of ZYVOX-treated and 14.1% of comparator-treated patients experienced at least one drug-related adverse event. For all other indications, 18.8% of ZYVOX-treated and 34.3% of comparator-treated patients experienced at least one drug-related adverse event.

Table 3 shows the incidence of all-causality, treatment-emergent adverse reactions reported in more than 1% of pediatric patients (and more than 1 patient) in either treatment group in the comparator-controlled Phase 3 trials.

Table 3. Incidence (%) of Treatment-Emergent Adverse Reactions Occurring in > 1% of Pediatric Patients (and >1 Patient) in Either Treatment Group in Comparator-Controlled Clinical Trials

Of the pediatric patients treated for uSSSIs, 1.6% of ZYVOX-treated and 2.4% of comparator-treated patients discontinued treatment due to drug-related adverse events. For all other indications, discontinuations due to drug-related adverse events occurred in 0.9% of ZYVOX-treated and 6.1% of comparator-treated patients.

Laboratory Abnormalities

ZYVOX has been associated with thrombocytopenia when used in doses up to and including 600 mg every 12 hours for up to 28 days. In Phase 3 comparator-controlled trials, the percentage of adult patients who developed a substantially low platelet count (defined as less than 75% of lower limit of normal and/or baseline) was 2.4% (range among studies: 0.3 to 10.0%) with ZYVOX and 1.5% (range among studies: 0.4 to 7.0%) with a comparator. In a study of hospitalized pediatric patients ranging in age from birth through 11 years, the percentage of patients who developed a substantially low platelet count (defined as less than 75% of lower limit of normal and/or baseline) was 12.9% with ZYVOX and 13.4% with vancomycin. In an outpatient study of pediatric patients aged from 5 through 17 years, the percentage of patients who developed a substantially low platelet count was 0% with ZYVOX and 0.4% with cefadroxil. Thrombocytopenia associated with the use of ZYVOX appears to be dependent on duration of therapy (generally greater than 2 weeks of treatment). The platelet counts for most patients returned to the normal range/baseline during the follow-up period. No related clinical adverse events were identified in Phase 3 clinical trials in patients developing thrombocytopenia. Bleeding events were identified in thrombocytopenic patients in a compassionate use program for ZYVOX; the role of linezolid in these events cannot be determined [see WARNINGS AND PRECAUTIONS].

Changes seen in other laboratory parameters, without regard to drug relationship, revealed no substantial differences between ZYVOX and the comparators. These changes were generally not clinically significant, did not lead to discontinuation of therapy, and were reversible. The incidence of adult and pediatric patients with at least one substantially abnormal hematologic or serum chemistry value is presented in Tables 4, 5, 6, and 7.

Table 4. Percent of Adult Patients who Experienced at Least One Substantially Abnormal* Hematology Laboratory Value in Comparator-Controlled Clinical Trials with ZYVOX

Table 5. Percent of Adult Patients who Experienced at Least One Substantially Abnormal* Serum Chemistry Laboratory Value in Comparator-Controlled Clinical Trials with ZYVOX

Table 6. Percent of Pediatric Patients who Experienced at Least One Substantially Abnormal* Hematology Laboratory Value in Comparator-Controlled Clinical Trials with ZYVOX

Table 7. Percent of Pediatric Patients who Experienced at Least One Substantially Abnormal* Serum Chemistry Laboratory Value in Comparator-Controlled Clinical Trials with ZYVOX

Postmarketing Experience

The following adverse reactions have been identified during postapproval use of ZYVOX. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Myelosuppression (including anemia, leukopenia, pancytopenia, and thrombocytopenia) has been reported during postmarketing use of ZYVOX [see WARNINGS AND PRECAUTIONS]. Peripheral neuropathy, and optic neuropathy sometimes progressing to loss of vision, have been reported in patients treated with ZYVOX [see WARNINGS AND PRECAUTIONS]. Lactic acidosis has been reported with the use of ZYVOX [see WARNINGS AND PRECAUTIONS]. Although these reports have primarily been in patients treated for longer than the maximum recommended duration of 28 days, these events have also been reported in patients receiving shorter courses of therapy. Serotoninsyndrome has been reported in patients receiving concomitant serotonergic agents, including antidepressants such as selective serotonin reuptake inhibitors (SSRIs) and ZYVOX [see WARNINGS AND PRECAUTIONS]. Convulsions have been reported with the use of ZYVOX [see WARNINGS AND PRECAUTIONS]. Anaphylaxis, angioedema, and bullous skin disorders such as those described as Stevens-Johnson syndrome have been reported. Superficial tooth discoloration and tongue discoloration have been reported with the use of linezolid. The tooth discoloration was removable with professional dental cleaning (manual descaling) in cases with known outcome. Hypoglycemia, including symptomatic episodes, has been reported [see WARNINGS AND PRECAUTIONS].

DRUG INTERACTIONS

Monoamine Oxidase Inhibitors

Linezolid is a reversible, nonselective inhibitor of monoamine oxidase. [see CONTRAINDICATIONSand CLINICAL PHARMACOLOGY].

Adrenergic And Serotonergic Agents

Linezolid has the potential for interaction with adrenergic and serotonergic agents. [see WARNINGS AND PRECAUTIONS and CLINICAL PHARMACOLOGY].

Warnings & Precautions

WARNINGS

Included as part of the "PRECAUTIONS" Section

PRECAUTIONS

Myelosuppression

Myelosuppression (including anemia, leukopenia, pancytopenia, and thrombocytopenia) has been reported in patients receiving linezolid. In cases where the outcome is known, when linezolid was discontinued, the affected hematologic parameters have risen toward pretreatment levels. Complete blood counts should be monitored weekly in patients who receive linezolid, particularly in those who receive linezolid for longer than two weeks, those with pre-existing myelosuppression, those receiving concomitant drugs that produce bone marrow suppression, or those with a chronic infection who have received previous or concomitant antibiotic therapy. Discontinuation of therapy with linezolid should be considered in patients who develop or have worsening myelosuppression.

Peripheral And Optic Neuropathy

Peripheral and optic neuropathies have been reported in patients treated with ZYVOX, primarily in those patients treated for longer than the maximum recommended duration of 28 days. In cases of optic neuropathy that progressed to loss of vision, patients were treated for extended periods beyond the maximum recommended duration. Visual blurring has been reported in some patients treated with ZYVOX for less than 28 days. Peripheral and optic neuropathy has also been reported in children.

If patients experience symptoms of visual impairment, such as changes in visual acuity, changes in color vision, blurred vision, or visual field defect, prompt ophthalmic evaluation is recommended. Visual function should be monitored in all patients taking ZYVOX for extended periods (≥ 3 months) and in all patients reporting new visual symptoms regardless of length of therapy with ZYVOX. If peripheral or optic neuropathy occurs, the continued use of ZYVOX in these patients should be weighed against the potential risks.

Serotonin Syndrome

Spontaneous reports of serotonin syndrome including fatal cases associated with the co-administration of ZYVOX and serotonergic agents, including antidepressants such as selective serotonin reuptake inhibitors (SSRIs), have been reported.

Unless clinically appropriate and patients are carefully observed for signs and/or symptoms of serotonin syndrome or neuroleptic malignant syndrome-like (NMS-like) reactions, linezolid should not be administered to patients with carcinoid syndrome and/or patients taking any of the following medications: serotonin re-uptake inhibitors, tricyclic antidepressants, serotonin 5-HT1 receptor agonists (triptans), meperidine, bupropion, or buspirone [see DRUG INTERACTIONS and CLINICAL PHARMACOLOGY].

In some cases, a patient already receiving a serotonergic antidepressant or buspirone may require urgent treatment with linezolid. If alternatives to linezolid are not available and the potential benefits of linezolid outweigh the risks of serotonin syndrome or NMS-like reactions, the serotonergic antidepressant should be stopped promptly and linezolid administered. The patient should be monitored for two weeks (five weeks if fluoxetine was taken) or until 24 hours after the last dose of linezolid, whichever comes first. Symptoms of serotonin syndrome or NMS-like reactions include hyperthermia, rigidity, myoclonus, autonomic instability, and mental status changes that include extreme agitation progressing to delirium and coma. The patient should also be monitored for discontinuation symptoms of the antidepressant (see package insert of the specified agent(s) for a description of the associated discontinuation symptoms).

Mortality Imbalance In An Investigational Study In Patients With Catheter-Related Bloodstream Infections, Including Those With Catheter-Site Infections

An imbalance in mortality was seen in patients treated with linezolid relative to vancomycin/dicloxacillin/oxacillin in an open-label study in seriously ill patients with intravascular catheter-related infections [78/363 (21.5%) vs. 58/363 (16.0%); odds ratio 1.426, 95% CI 0.970, 2.098]. While causality has not been established, this observed imbalance occurred primarily in linezolid-treated patients in whom either Gram-negative pathogens, mixed Gram-negative and Gram-positive pathogens, or no pathogen were identified at baseline, but was not seen in patients with Gram-positive infections only.

Linezolid is not approved and should not be used for the treatment of patients with catheter-related bloodstream infections or catheter-site infections.

Linezolid has no clinical activity against Gram-negative pathogens and is not indicated for the treatment of Gram-negative infections. It is critical that specific Gram-negative therapy be initiated immediately if a concomitant Gram-negative pathogen is documented or suspected [see INDICATIONS].

Clostridium Difficile Associated Diarrhea

Clostridium difficile associated diarrhea (CDAD) has been reported with use of nearly all antibacterialagents, including ZYVOX, and may range in severity from mild diarrhea to fatal colitis. Treatment with antibacterial agents alters the normal flora of the colon leading to overgrowth of C. difficile.

C. difficile produces toxins A and B which contribute to the development of CDAD. Hypertoxin producing strains of C. difficile cause increased morbidity and mortality, as these infections can be refractory to antimicrobial therapy and may require colectomy. CDAD must be considered in all patients who present with diarrhea following antibiotic use.

Careful medical history is necessary since CDAD has been reported to occur over two months after the administration of antibacterial agents.

If CDAD is suspected or confirmed, ongoing antibiotic use not directed against C. difficile may need to be discontinued. Appropriate fluid and electrolyte management, protein supplementation, antibiotic treatment of C. difficile, and surgical evaluation should be instituted as clinically indicated.

Potential Interactions Producing Elevation Of Blood Pressure

Unless patients are monitored for potential increases in blood pressure, linezolid should not be administered to patients with uncontrolled hypertension, pheochromocytoma, thyrotoxicosis and/or patients taking any of the following types of medications: directly and indirectly acting sympathomimetic agents (e.g., pseudoephedrine), vasopressive agents (e.g., epinephrine, norepinephrine), dopaminergic agents (e.g., dopamine, dobutamine) [see DRUG INTERACTIONS and CLINICAL PHARMACOLOGY].

Lactic Acidosis

Lactic acidosis has been reported with the use of ZYVOX. In reported cases, patients experienced repeated episodes of nausea and vomiting. Patients who develop recurrent nausea or vomiting, unexplained acidosis, or a low bicarbonate level while receiving ZYVOX should receive immediate medical evaluation.

Convulsions

Convulsions have been reported in patients when treated with linezolid. In some of these cases, a history of seizures or risk factors for seizures was reported.

Hypoglycemia

Postmarketing cases of symptomatic hypoglycemia have been reported in patients with diabetes mellitus receiving insulin or oral hypoglycemic agents when treated with linezolid, a reversible, nonselective MAO inhibitor. Some MAO inhibitors have been associated with hypoglycemic episodes in diabetic patients receiving insulin or hypoglycemic agents. While a causal relationship between linezolid and hypoglycemia has not been established, diabetic patients should be cautioned of potential hypoglycemic reactions when treated with linezolid.

If hypoglycema occurs, a decrease in the dose of insulin or oral hypoglycemic agent, or discontinuation of oral hypoglycemic agent, insulin, or linezolid may be required.

Development Of Drug-Resistant Bacteria

Prescribing ZYVOX in the absence of a proven or strongly suspected bacterial infection or a prophylactic indication is unlikely to provide benefit to the patient and increases the risk of the development of drug-resistant bacteria.

Nonclinical Toicology

Carcinogenesis, Mutagenesis, Impairment Of Fertility

Lifetime studies in animals have not been conducted to evaluate the carcinogenic potential of linezolid. Neither mutagenic nor clastogenic potential was found in a battery of tests including: assays for mutagenicity (Ames bacterial reversion and CHO cell mutation), an in vitro unscheduled DNA synthesis (UDS) assay, an in vitro chromosome aberration assay in human lymphocytes, and an in vivo mouse micronucleus assay.

Linezolid did not affect the fertility or reproductive performance of adult female rats. It reversibly decreased fertility and reproductive performance in adult male rats when given at doses ≥ 50 mg/kg/day, with exposures approximately equal to or greater than the expected human exposure level (exposure comparisons are based on AUCs). The reversible fertility effects were mediated through altered spermatogenesis. Affected spermatids contained abnormally formed and oriented mitochondria and were non-viable. Epithelial cell hypertrophy and hyperplasia in the epididymis was observed in conjunction with decreased fertility. Similar epididymal changes were not seen in dogs.

In sexually mature male rats exposed to drug as juveniles, mildly decreased fertility was observed following treatment with linezolid through most of their period of sexual development (50 mg/kg/day from days 7 to 36 of age, and 100 mg/kg/day from days 37 to 55 of age), with exposures up to 1.7-fold greater than mean AUCs observed in pediatric patients aged 3 months to 11 years. Decreased fertility was not observed with shorter treatment periods, corresponding to exposure in utero through the early neonatal period (gestation day 6 through postnatal day 5), neonatal exposure (postnatal days 5 to 21), or to juvenile exposure (postnatal days 22 to 35). Reversible reductions in sperm motility and altered sperm morphology were observed in rats treated from postnatal day 22 to 35.

Use In Specific Populations

Pregnancy

Teratogenic Effects – Pregnancy Category C

Linezolid was not teratogenic in mice, rats, or rabbits at exposure levels 6.5-fold (in mice), equivalent to (in rats), or 0.06-fold (in rabbits) the expected human exposure level, based on AUCs. However, embryo and fetal toxicities were seen (see Non-Teratogenic Effects). There are no adequate and well-controlled studies in pregnant women. ZYVOX should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Non-Teratogenic Effects

In mice, embryo and fetal toxicities were seen only at doses that caused maternal toxicity (clinical signs and reduced body weight gain). A dose of 450 mg/kg/day (6.5-fold the estimated human exposure level based on AUCs) correlated with increased postimplantational embryo death, including total litter loss, decreased fetal body weights, and an increased incidence of costal cartilage fusion.

In rats, mild fetal toxicity was observed at 15 and 50 mg/kg/day (exposure levels 0.22-fold to approximately equivalent to the estimated human exposure, respectively, based on AUCs). The effects consisted of decreased fetal body weights and reduced ossification of sternebrae, a finding often seen in association with decreased fetal body weights. Slight maternal toxicity, in the form of reduced body weight gain, was seen at 50 mg/kg/day.

In rabbits, reduced fetal body weight occurred only in the presence of maternal toxicity (clinical signs, reduced body weight gain and food consumption) when administered at a dose of 15 mg/kg/day (0.06-fold the estimated human exposure based on AUCs).

When female rats were treated with 50 mg/kg/day (approximately equivalent to the estimated human exposure based on AUCs) of linezolid during pregnancy and lactation, survival of pups was decreased on postnatal days 1 to 4. Male and female pups permitted to mature to reproductive age, when mated, showed an increase in preimplantation loss.

Nursing Mothers

Linezolid and its metabolites are excreted in the milk of lactating rats. Concentrations in milk were similar to those in maternal plasma. It is not known whether linezolid is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when ZYVOX is administered to a nursing woman.

Pediatric Use

The safety and effectiveness of ZYVOX for the treatment of pediatric patients with the following infections are supported by evidence from adequate and well-controlled studies in adults, pharmacokinetic data in pediatric patients, and additional data from a comparator-controlled study of Gram-positive infections in pediatric patients ranging in age from birth through 11 years [see INDICATIONS , CLINICAL PHARMACOLOGY and Clinical Studies]:

· nosocomial pneumonia

· complicated skin and skin structure infections

· community-acquired pneumonia (also supported by evidence from an uncontrolled study in patients ranging in age from 8 months through 12 years)

· vancomycin-resistant Enterococcus faecium infections

The safety and effectiveness of ZYVOX for the treatment of pediatric patients with the following infection have been established in a comparator-controlled study in pediatric patients ranging in age from 5 through 17 years [see Clinical Studies]:

· uncomplicated skin and skin structure infections caused by Staphylococcus aureus(methicillin-susceptible strains only) or Streptococcus pyogenes

Pharmacokinetic information generated in pediatric patients with ventriculoperitoneal shunts showed variable cerebrospinal fluid (CSF) linezolid concentrations following single and multiple dosing of linezolid; therapeutic concentrations were not consistently achieved or maintained in the CSF. Therefore, the use of linezolid for the empiric treatment of pediatric patients with central nervous system infections is not recommended.

The pharmacokinetics of linezolid have been evaluated in pediatric patients from birth to 17 years of age. In general, weight-based clearance of linezolid gradually decreases with increasing age of pediatric patients. However, in preterm (gestational age < 34 weeks) neonates < 7 days of age, linezolid clearance is often lower than in full-term neonates < 7 days of age. Consequently, preterm neonates < 7 days of age may need an alternative linezolid dosing regimen of 10 mg/kg every 12 hours [see DOSAGE AND ADMINISTRATION and CLINICAL PHARMACOLOGY].

In limited clinical experience, 5 out of 6 (83%) pediatric patients with infections due to Gram-positive pathogens with minimum inhibitory concentrations (MICs) of 4 mcg/mL treated with ZYVOX had clinical cures. However, pediatric patients exhibit wider variability in linezolid clearance and systemic exposure (AUC) compared with adults. In pediatric patients with a sub-optimal clinical response, particularly those with pathogens with MIC of 4 mcg/mL, lower systemic exposure, site and severity of infection, and the underlying medical condition should be considered when assessing clinical response [see CLINICAL PHARMACOLOGY and DOSAGE AND ADMINISTRATION].

Geriatric Use

Of the 2046 patients treated with ZYVOX in Phase 3 comparator-controlled clinical trials, 589 (29%) were 65 years or older and 253 (12%) were 75 years or older. No overall differences in safety or effectiveness were observed between these patients and younger patients, and other reported clinical experience has not identified differences in responses between the elderly and younger patients, but greater sensitivity of some older individuals cannot be ruled out.

Overdosage & Contraindications

OVERDOSE

In the event of overdosage, supportive care is advised, with maintenance of glomerular filtration. Hemodialysis may facilitate more rapid elimination of linezolid. In a Phase 1 clinical trial, approximately 30% of a dose of linezolid was removed during a 3-hour hemodialysis session beginning 3 hours after the dose of linezolid was administered. Data are not available for removal of linezolid with peritoneal dialysis or hemoperfusion. Clinical signs of acute toxicity in animals were decreased activity and ataxia in rats and vomiting and tremors in dogs treated with 3000 mg/kg/day and 2000 mg/kg/day, respectively.

CONTRAINDICATIONS

Hypersensitivity

ZYVOX formulations are contraindicated for use in patients who have known hypersensitivity to linezolid or any of the other product components.

Monoamine Oxidase Inhibitors

Linezolid should not be used in patients taking any medicinal product which inhibits monoamine oxidases A or B (e.g., phenelzine, isocarboxazid) or within two weeks of taking any such medicinal product.

Clinical Pharmacology

CLINICAL PHARMACOLOGY

Mechanism Of Action

ZYVOX is an antibacterial drug [see Microbiology].

Pharmacodynamics

In a randomized, positive- and placebo-controlled crossover thorough QT study, 40 healthy subjects were administered a single ZYVOX 600 mg dose via a 1 hour IV infusion, a single ZYVOX 1200 mg dose via a 1 hour IV infusion, placebo, and a single oral dose of positive control. At both the 600 mg and 1200 mg ZYVOX doses, no significant effect on QTc interval was detected at peak plasma concentration or at any other time.

Pharmacokinetics

The mean pharmacokinetic parameters of linezolid in adults after single and multiple oral and intravenous doses are summarized in Table 8. Plasma concentrations of linezolid at steady-state after oral doses of 600 mg given every 12 hours are shown in Figure 1.

Table 8. Mean (Standard Deviation) Pharmacokinetic Parameters of Linezolid in Adults

Figure 1. Plasma Concentrations of Linezolid in Adults at Steady-State Following Oral Dosing Every 12 Hours (Mean ± Standard Deviation, n=16)

Absorption

Linezolid is extensively absorbed after oral dosing. Maximum plasma concentrations are reached approximately 1 to 2 hours after dosing, and the absolute bioavailability is approximately 100%. Therefore, linezolid may be given orally or intravenously without dose adjustment.

Linezolid may be administered without regard to the timing of meals. The time to reach the maximum concentration is delayed from 1.5 hours to 2.2 hours and Cmax is decreased by about 17% when high fat food is given with linezolid. However, the total exposure measured as AUC0-∞ is similar under both conditions.

Distribution

Animal and human pharmacokinetic studies have demonstrated that linezolid readily distributes to well-perfused tissues. The plasma protein binding of linezolid is approximately 31% and is concentration-independent. The volume of distribution of linezolid at steady-state averaged 40 to 50 liters in healthy adult volunteers.

Linezolid concentrations have been determined in various fluids from a limited number of subjects in Phase 1 volunteer studies following multiple dosing of linezolid. The ratio of linezolid in saliva relative to plasma was 1.2 to 1 and the ratio of linezolid in sweat relative to plasma was 0.55 to 1.

Metabolism

Linezolid is primarily metabolized by oxidation of the morpholine ring, which results in two inactive ring-opened carboxylic acid metabolites: the aminoethoxyacetic acid metabolite (A), and the hydroxyethyl glycine metabolite (B). Formation of metabolite A is presumed to be formed via an enzymatic pathway whereas metabolite B is mediated by a non-enzymatic chemical oxidation mechanism in vitro. In vitro studies have demonstrated that linezolid is minimally metabolized and may be mediated by human cytochrome P450. However, the metabolic pathway of linezolid is not fully understood.

Excretion

Nonrenal clearance accounts for approximately 65% of the total clearance of linezolid. Under steady-state conditions, approximately 30% of the dose appears in the urine as linezolid, 40% as metabolite B, and 10% as metabolite A. The mean renal clearance of linezolid is 40 mL/min which suggests net tubular reabsorption. Virtually no linezolid appears in the feces, while approximately 6% of the dose appears in the feces as metabolite B, and 3% as metabolite A.

A small degree of nonlinearity in clearance was observed with increasing doses of linezolid, which appears to be due to lower renal and nonrenal clearance of linezolid at higher concentrations. However, the difference in clearance was small and was not reflected in the apparent elimination half-life.

Specific Populations

Geriatric Patients

The pharmacokinetics of linezolid are not significantly altered in elderly patients (65 years or older). Therefore, dose adjustment for geriatric patients is not necessary.

Pediatric Patients

The pharmacokinetics of linezolid following a single intravenous dose were investigated in pediatric patients ranging in age from birth through 17 years (including premature and full-term neonates), in healthy adolescent subjects ranging in age from 12 through 17 years, and in pediatric patients ranging in age from 1 week through 12 years. The pharmacokinetic parameters of linezolid are summarized in Table 9 for the pediatric populations studied and healthy adult subjects after administration of single intravenous doses.

The Cmax and the volume of distribution (Vss) of linezolid are similar regardless of age in pediatric patients. However, plasma clearance of linezolid varies as a function of age. With the exclusion of pre-term neonates less than one week of age, weight-based clearance is most rapid in the youngest age groups ranging from < 1 week old to 11 years, resulting in lower single-dose systemic exposure (AUC) and a shorter half-life as compared with adults. As the age of pediatric patients increases, the weight-based clearance of linezolid gradually decreases, and by adolescence mean clearance values approach those observed for the adult population. There is increased inter-subject variability in linezolid clearance and systemic drug exposure (AUC) across all pediatric age groups as compared with adults.

Similar mean daily AUC values were observed in pediatric patients from birth to 11 years of age dosed every 8 hours relative to adolescents or adults dosed every 12 hours. Therefore, the dosage for pediatric patients up to 11 years of age should be 10 mg/kg every 8 hours. Pediatric patients 12 years and older should receive 600 mg every 12 hours [see DOSAGE AND ADMINISTRATION].

Table 9. Pharmacokinetic Parameters of Linezolid in Pediatrics and Adults Following a Single Intravenous Infusion of 10 mg/kg or 600 mg Linezolid (Mean: (%CV); [Min, Max Values])

Gender

Females have a slightly lower volume of distribution of linezolid than males. Plasma concentrations are higher in females than in males, which is partly due to body weight differences. After a 600-mg dose, mean oral clearance is approximately 38% lower in females than in males. However, there are no significant gender differences in mean apparent elimination-rate constant or half-life. Thus, drug exposure in females is not expected to substantially increase beyond levels known to be well tolerated. Therefore, dose adjustment by gender does not appear to be necessary.

Renal Impairment

The pharmacokinetics of the parent drug, linezolid, are not altered in patients with any degree of renal impairment; however, the two primary metabolites of linezolid accumulate in patients with renal impairment, with the amount of accumulation increasing with the severity of renal dysfunction (see Table 10). The pharmacokinetics of linezolid and its two metabolites have also been studied in patients with end-stage renal disease (ESRD) receiving hemodialysis. In the ESRD study, 14 patients were dosed with linezolid 600 mg every 12 hours for 14.5 days (see Table 11). Because similar plasma concentrations of linezolid are achieved regardless of renal function, no dose adjustment is recommended for patients with renal impairment. However, given the absence of information on the clinical significance of accumulation of the primary metabolites, use of linezolid in patients with renal impairment should be weighed against the potential risks of accumulation of these metabolites. Both linezolid and the two metabolites are eliminated by hemodialysis. No information is available on the effect of peritoneal dialysis on the pharmacokinetics of linezolid. Approximately 30% of a dose was eliminated in a 3-hour hemodialysis session beginning 3 hours after the dose of linezolid was administered; therefore, linezolid should be given after hemodialysis.

Table 10. Mean (Standard Deviation) AUCs and Elimination Half-lives of Linezolid and Metabolites A and B in Patients with Varying Degrees of Renal Impairment After a Single 600 mg Oral Dose of Linezolid

Table 11. Mean (Standard Deviation) AUCs and Elimination Half-lives of Linezolid and Metabolites A and B in Subjects with End-Stage Renal Disease (ESRD) After the Administration of 600 mg Linezolid Every 12 Hours for 14.5 Days

Hepatic Impairment

The pharmacokinetics of linezolid are not altered in patients (n=7) with mild-to-moderate hepatic impairment (Child-Pugh class A or B). On the basis of the available information, no dose adjustment is recommended for patients with mild-to-moderate hepatic impairment. The pharmacokinetics of linezolid in patients with severe hepatic impairment have not been evaluated.

Drug Interactions

Drugs Metabolized By Cytochrome P450

Linezolid is not an inducer of cytochrome P450 (CYP450) in rats. In addition, linezolid does not inhibit the activities of clinically significant human CYP isoforms (e.g., 1A2, 2C9, 2C19, 2D6, 2E1, 3A4). Therefore, linezolid is not expected to affect the pharmacokinetics of other drugs metabolized by these major enzymes. Concurrent administration of linezolid does not substantially alter the pharmacokinetic characteristics of (S)-warfarin, which is extensively metabolized by CYP2C9. Drugs such as warfarin and phenytoin, which are CYP2C9 substrates, may be given with linezolid without changes in dosage regimen.

Antibiotics

Aztreonam: The pharmacokinetics of linezolid or aztreonam are not altered when administered together.

Gentamicin: The pharmacokinetics of linezolid or gentamicin are not altered when administered together.

Antioxidants

The potential for drug-drug interactions with linezolid and the antioxidants Vitamin C and Vitamin Ewas studied in healthy volunteers. Subjects were administered a 600 mg oral dose of linezolid on Day 1, and another 600 mg dose of linezolid on Day 8. On Days 2-9, subjects were given either Vitamin C (1000 mg/day) or Vitamin E (800 IU/ day). The AUC0-∞ of linezolid increased 2.3% when co-administered with Vitamin C and 10.9% when co-administered with Vitamin E. No linezolid dose adjustment is recommended during co-administration with Vitamin C or Vitamin E.

Strong CYP 3A4 Inducers

Rifampin: The effect of rifampin on the pharmacokinetics of linezolid was evaluated in a study of 16 healthy adult males. Volunteers were administered oral linezolid 600 mg twice daily for 5 doses with and without rifampin 600 mg once daily for 8 days. Co-administration of rifampin with linezolid resulted in a 21% decrease in linezolid Cmax [90% CI, 15% - 27%] and a 32% decrease in linezolid AUC0-12 [90% CI, 27% - 37%]. The clinical significance of this interaction is unknown. The mechanism of this interaction is not fully understood and may be related to the induction of hepatic enzymes. Other strong inducers of hepatic enzymes (e.g. carbamazepine, phenytoin, phenobarbital) could cause a similar or smaller decrease in linezolid exposure.

Monoamine Oxidase Inhibition

Linezolid is a reversible, nonselective inhibitor of monoamine oxidase. Therefore, linezolid has the potential for interaction with adrenergic and serotonergic agents.

Adrenergic Agents

Some individuals receiving ZYVOX may experience a reversible enhancement of the pressorresponse to indirect-acting sympathomimetic agents, vasopressor or dopaminergic agents. Commonly used drugs such as phenylpropanolamine and pseudoephedrine have been specifically studied. Initial doses of adrenergic agents, such as dopamine or epinephrine, should be reduced and titrated to achieve the desired response.

Tyramine: A significant pressor response has been observed in normal adult subjects receiving linezolid and tyramine doses of more than 100 mg. Therefore, patients receiving linezolid need to avoid consuming large amounts of foods or beverages with high tyramine content [see PATIENT INFORMATION].

Pseudoephedrine HCl or phenylpropanolamine HCl: A reversible enhancement of the pressor response of either pseudoephedrine HCl (PSE) or phenylpropanolamine HCl (PPA) is observed when linezolid is administered to healthy normotensive subjects [see WARNINGS AND PRECAUTIONS and DRUG INTERACTIONS]. A similar study has not been conducted in hypertensive patients. The interaction studies conducted in normotensive subjects evaluated the blood pressure and heart rate effects of placebo, PPA or PSE alone, linezolid alone, and the combination of steady-state linezolid (600 mg every 12 hours for 3 days) with two doses of PPA (25 mg) or PSE (60 mg) given 4 hours apart. Heart rate was not affected by any of the treatments. Blood pressure was increased with both combination treatments. Maximum blood pressure levels were seen 2 to 3 hours after the second dose of PPA or PSE, and returned to baseline 2 to 3 hours after peak. The results of the PPA study follow, showing the mean (and range) maximum systolic blood pressure in mm Hg: placebo = 121 (103 to 158); linezolid alone = 120 (107 to 135); PPA alone = 125 (106 to 139); PPA with linezolid = 147 (129 to 176). The results from the PSE study were similar to those in the PPA study. The mean maximum increase in systolic blood pressure over baseline was 32 mm Hg (range: 20-52 mm Hg) and 38 mm Hg (range: 18-79 mm Hg) during co-administration of linezolid with pseudoephedrine or phenylpropanolamine, respectively.

Serotonergic Agents

Dextromethorphan: The potential drug-drug interaction with dextromethorphan was studied in healthy volunteers. Subjects were administered dextromethorphan (two 20-mg doses given 4 hours apart) with or without linezolid. No serotonin syndrome effects (confusion, delirium, restlessness, tremors, blushing, diaphoresis, hyperpyrexia) have been observed in normal subjects receiving linezolid and dextromethorphan.

Microbiology

Mechanism Of Action

Linezolid is a synthetic antibacterial agent of the oxazolidinone class, which has clinical utility in the treatment of infections caused by aerobic Gram-positive bacteria. The in vitro spectrum of activity of linezolid also includes certain Gram-negative bacteria and anaerobic bacteria. Linezolid binds to a site on the bacterial 23S ribosomal RNA of the 50S subunit and prevents the formation of a functional 70S initiation complex, which is essential for bacterial reproduction. The results of time-kill studies have shown linezolid to be bacteriostatic against enterococci and staphylococci. For streptococci, linezolid was found to be bactericidal for the majority of isolates.

Mechanisms Of Resistance

In vitro studies have shown that point mutations in the 23S rRNA are associated with linezolid resistance. Reports of vancomycin-resistant Enterococcus faecium becoming resistant to linezolid during its clinical use have been published. There are reports of Staphylococcus aureus (methicillin-resistant) developing resistance to linezolid during clinical use. The linezolid resistance in these organisms is associated with a point mutation in the 23S rRNA (substitution of thymine for guanineat position 2576) of the organism. Organisms resistant to oxazolidinones via mutations in chromosomal genes encoding 23S rRNA or ribosomal proteins (L3 and L4) are generally cross-resistant to linezolid. Also linezolid resistance in staphylococci mediated by the enzyme methyltransferase has been reported. This resistance is mediated by the cfr (chloramphenicol-florfenicol) gene located on a plasmid which is transferable between staphylococci.

Interaction With Other Antimicrobial Drugs

In vitro studies have demonstrated additivity or indifference between linezolid and vancomycin, gentamicin, rifampin, imipenem-cilastatin, aztreonam, ampicillin, or streptomycin.

Linezolid has been shown to be active against most isolates of the following microorganisms, both in vitro and in clinical infections [see INDICATIONS].

Gram-Positive Bacteria

Enterococcus faecium (vancomycin-resistant isolates only)
Staphylococcus aureus (including methicillin-resistant isolates)
Streptococcus agalactiae
Streptococcus pneumoniae
Streptococcus pyogenes

The following in vitro data are available, but their clinical significance is unknown. Greater than 90% of the following bacteria exhibit an in vitro MIC less than or equal to the linezolid-susceptible breakpoint for organisms of similar genus shown in Table 12. The safety and effectiveness of linezolid in treating clinical infections due to these bacteria have not been established in adequate and well-controlled clinical trials.

Gram-Positive Bacteria

Enterococcus faecalis (including vancomycin-resistant isolates)
Enterococcus faecium (vancomycin-susceptible isolates)
Staphylococcus epidermidis (including methicillin-resistant isolates)
Staphylococcus haemolyticus
Viridans group streptococci

Gram-Negative Bacteria

Pasteurella multocida

Susceptibility Test Methods

When available, the clinical microbiology laboratory should provide the results of in vitrosusceptibility test results for antimicrobial drug products used in local hospitals and practice areas to the physician as periodic reports that describe the susceptibility profile of nosocomial and community-acquired pathogens. These reports should aid the physician in selecting an antibacterial drug product for treatment.

Dilution Techniques

Quantitative methods are used to determine antimicrobial minimum inhibitory concentrations (MICs). These MICs provide estimates of the susceptibility of bacteria to antimicrobial compounds. The MICs should be determined using a standardized method1,2 (broth and/or agar). The MIC values should be interpreted according to criteria provided in Table 12.

Diffusion Techniques

Quantitative methods that require measurement of zone diameters can also provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds. The zone size provides an estimate of the susceptibility of bacteria to antimicrobial compounds. The zone size should be determined using a standardized test method2,3. This procedure uses paper disks impregnated with 30 mcg linezolid to test the susceptibility of bacteria to linezolid. The disk diffusion interpretive criteria are provided in Table 12.

Table 12. Susceptibility Test Interpretive Criteria for Linezolid

A report of “Susceptible” indicates that the antimicrobial drug is likely to inhibit growth of the pathogen if the antimicrobial drug reaches the concentration usually achievable at the site of infection. A report of “Intermediate” indicates that the result should be considered equivocal, and, if the bacteria is not fully susceptible to alternative, clinically feasible drugs, the test should be repeated. This category implies possible clinical applicability in body sites where the drug product is physiologically concentrated or in situations where a high dosage of the drug product can be used. This category also provides a buffer zone that prevents small uncontrolled technical factors from causing major discrepancies in interpretation. A report of “Resistant” indicates that the antimicrobial is not likely to inhibit growth of the pathogen if the antimicrobial drug reaches the concentration usually achievable at the site of infection; other therapy should be selected.

Quality Control

Standardized susceptibility test procedures require the use of laboratory controls to monitor and ensure the accuracy and precision of supplies and reagents used in the assay, and the techniques of the individuals performing the test1,2,3. Standard linezolid powder should provide the following range of MIC values noted in Table 13. For the diffusion technique using the 30 mcg linezolid disk, the criteria in Table 13 should be achieved.

Table 13. Acceptable Quality Control Ranges for Linezolid

Animal Toxicology And/Or Pharmacology

Target organs of linezolid toxicity were similar in juvenile and adult rats and dogs. Dose- and time-dependent myelosuppression, as evidenced by bone marrow hypocellularity/decreased hematopoiesis, decreased extramedullary hematopoiesis in spleen and liver, and decreased levels of circulating erythrocytes, leukocytes, and platelets have been seen in animal studies. Lymphoiddepletion occurred in thymus, lymph nodes, and spleen. Generally, the lymphoid findings were associated with anorexia, weight loss, and suppression of body weight gain, which may have contributed to the observed effects.

In rats administered linezolid orally for 6 months, non-reversible, minimal to mild axonal degeneration of sciatic nerves was observed at 80 mg/kg/day; minimal degeneration of the sciatic nerve was also observed in 1 male at this dose level at a 3-month interim necropsy. Sensitive morphologic evaluation of perfusion-fixed tissues was conducted to investigate evidence of optic nerve degeneration. Minimal to moderate optic nerve degeneration was evident in 2 male rats after 6 months of dosing, but the direct relationship to drug was equivocal because of the acute nature of the finding and its asymmetrical distribution. The nerve degeneration observed was microscopically comparable to spontaneous unilateral optic nerve degeneration reported in aging rats and may be an exacerbation of common background change.

These effects were observed at exposure levels that are comparable to those observed in some human subjects. The hematopoietic and lymphoid effects were reversible, although in some studies, reversal was incomplete within the duration of the recovery period.

Clinical Studies

Adults

Nosocomial Pneumonia

Adult patients with clinically and radiologically documented nosocomial pneumonia were enrolled in a randomized, multi-center, double-blind trial. Patients were treated for 7 to 21 days. One group received ZYVOX I.V. Injection 600 mg every 12 hours, and the other group received vancomycin 1 g every 12 hours intravenously. Both groups received concomitant aztreonam (1 to 2 g every 8 hours intravenously), which could be continued if clinically indicated. There were 203 linezolid-treated and 193 vancomycin-treated patients enrolled in the study. One hundred twenty-two (60%) linezolid-treated patients and 103 (53%) vancomycin-treated patients were clinically evaluable. The cure rates in clinically evaluable patients were 57% for linezolid-treated patients and 60% for vancomycintreated patients. The cure rates in clinically evaluable patients with ventilator-associated pneumonia were 47% for linezolid-treated patients and 40% for vancomycin-treated patients. A modified intent-to-treat (MITT) analysis of 94 linezolid-treated patients and 83 vancomycin-treated patients included subjects who had a pathogen isolated before treatment. The cure rates in the MITT analysis were 57% in linezolid-treated patients and 46% in vancomycintreated patients. The cure rates by pathogen for microbiologically evaluable patients are presented in Table 14.

Table 14. Cure Rates at the Test-of-Cure Visit for Microbiologically Evaluable

Complicated Skin And Skin Structure Infections

Adult patients with clinically documented complicated skin and skin structure infections were enrolled in a randomized, multi-center, double-blind, double-dummy trial comparing study medications administered intravenously followed by medications given orally for a total of 10 to 21 days of treatment. One group of patients received ZYVOX I.V. Injection 600 mg every 12 hours followed by ZYVOX Tablets 600 mg every 12 hours; the other group received oxacillin 2 g every 6 hours intravenously followed by dicloxacillin 500 mg every 6 hours orally. Patients could receive concomitant aztreonam if clinically indicated. There were 400 linezolid-treated and 419 oxacillin-treated patients enrolled in the study. Two hundred forty-five (61%) linezolid-treated patients and 242 (58%) oxacillin-treated patients were clinically evaluable. The cure rates in clinically evaluable patients were 90% in linezolid-treated patients and 85% in oxacillin-treated patients. A modified intent-to-treat (MITT) analysis of 316 linezolid-treated patients and 313 oxacillin-treated patients included subjects who met all criteria for study entry. The cure rates in the MITT analysis were 86% in linezolid-treated patients and 82% in oxacillin-treated patients. The cure rates by pathogen for microbiologically evaluable patients are presented in Table 15.

Table 15. Cure Rates at the Test-of-Cure Visit for MicrobiologicallyEvaluable Adult Patients with Complicated Skin and Skin Structure Infections

A separate study provided additional experience with the use of ZYVOX in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections. This was a randomized, open-label trial in hospitalized adult patients with documented or suspected MRSA infection.

One group of patients received ZYVOX I.V. Injection 600 mg every 12 hours followed by ZYVOX Tablets 600 mg every 12 hours. The other group of patients received vancomycin 1 g every 12 hours intravenously. Both groups were treated for 7 to 28 days, and could receive concomitant aztreonam or gentamicin if clinically indicated. The cure rates in microbiologically evaluable patients with MRSA skin and skin structure infection were 26/33 (79%) for linezolid-treated patients and 24/33 (73%) for vancomycin-treated patients.

Diabetic Foot Infections

Adult diabetic patients with clinically documented complicated skin and skin structure infections (“diabetic foot infections”) were enrolled in a randomized (2:1 ratio), multi-center, open-label trial comparing study medications administered intravenously or orally for a total of 14 to 28 days of treatment. One group of patients received ZYVOX 600 mg every 12 hours intravenously or orally; the other group received ampicillin/sulbactam 1.5 to 3 g intravenously or amoxicillin/clavulanate 500 to 875 mg every 8 to 12 hours orally. In countries where ampicillin/sulbactam is not marketed, amoxicillin/clavulanate 500 mg to 2 g every 6 hours was used for the intravenous regimen. Patients in the comparator group could also be treated with vancomycin 1 g every 12 hours intravenously if MRSA was isolated from the foot infection. Patients in either treatment group who had Gram-negative bacilli isolated from the infection site could also receive aztreonam 1 to 2 g every 8-12 hours intravenously. All patients were eligible to receive appropriate adjunctive treatment methods, such as debridement and off-loading, as typically required in the treatment of diabetic foot infections, and most patients received these treatments. There were 241 linezolid-treated and 120 comparator-treated patients in the intent-to-treat (ITT) study population. Two hundred twelve (86%) linezolid-treated patients and 105 (85%) comparator-treated patients were clinically evaluable. In the ITT population, the cure rates were 68.5% (165/241) in linezolid-treated patients and 64% (77/120) in comparator-treated patients, where those with indeterminate and missing outcomes were considered failures. The cure rates in the clinically evaluable patients (excluding those with indeterminate and missing outcomes) were 83% (159/192) and 73% (74/101) in the linezolid- and comparator-treated patients, respectively. A critical post-hoc analysis focused on 121 linezolid-treated and 60 comparator-treated patients who had a Gram-positive pathogen isolated from the site of infection or from blood, who had less evidence of underlying osteomyelitis than the overall study population, and who did not receive prohibited antimicrobials. Based upon that analysis, the cure rates were 71% (86/121) in the linezolid-treated patients and 63% (38/60) in the comparator-treated patients. None of the above analyses were adjusted for the use of adjunctive therapies. The cure rates by pathogen for microbiologically evaluable patients are presented in Table 16.

Table 16. Cure Rates at the Test-of-Cure Visit for Microbiologically Evaluable Adult Patients with Diabetic Foot Infections

Vancomycin-Resistant Enterococcal Infections

Adult patients with documented or suspected vancomycin-resistant enterococcal infection were enrolled in a randomized, multi-center, double-blind trial comparing a high dose of ZYVOX (600 mg) with a low dose of ZYVOX (200 mg) given every 12 hours either intravenously (IV) or orally for 7 to 28 days. Patients could receive concomitant aztreonam or aminoglycosides. There were 79 patients randomized to high-dose linezolid and 66 to low-dose linezolid. The intent-to-treat (ITT) population with documented vancomycin-resistant enterococcal infection at baseline consisted of 65 patients in the high-dose arm and 52 in the low-dose arm.

The cure rates for the ITT population with documented vancomycin-resistant enterococcal infection at baseline are presented in Table 17 by source of infection. These cure rates do not include patients with missing or indeterminate outcomes. The cure rate was higher in the high-dose arm than in the low-dose arm, although the difference was not statistically significant at the 0.05 level.

Table 17. Cure Rates at the Test-of-Cure Visit for ITT Adult Patients with Documented Vancomycin-Resistant Enterococcal Infections at Baseline

Pediatric Patients

Infections Due To Gram-Positive Bacteria

A safety and efficacy study provided experience on the use of ZYVOX in pediatric patients for the treatment of nosocomial pneumonia, complicated skin and skin structure infections, and other infections due to Gram-positive bacterial pathogens, including methicillin-resistant and -susceptible Staphylococcus aureus and vancomycinresistant Enterococcus faecium. Pediatric patients ranging in age from birth through 11 years with infections caused by the documented or suspected Gram-positive bacteria were enrolled in a randomized, open-label, comparator-controlled trial. One group of patients received ZYVOX I.V. Injection 10 mg/kg every 8 hours followed by ZYVOX for Oral Suspension 10 mg/kg every 8 hours. A second group received vancomycin 10 to 15 mg/kg intravenously every 6 to 24 hours, depending on age and renal clearance. Patients who had confirmed VRE infections were placed in a third arm of the study and received ZYVOX 10 mg/kg every 8 hours intravenously and/or orally. All patients were treated for a total of 10 to 28 days and could receive concomitant Gram-negative antibiotics if clinically indicated. In the intent-to-treat (ITT) population, there were 206 patients randomized to linezolid and 102 patients randomized to vancomycin. The cure rates for ITT, MITT, and clinically evaluable patients are presented in Tabl 18. After the study was completed, 13 additional patients ranging from 4 days through 16 years of age were enrolled in an open-label extension of the VRE arm of the study. Table 19 provides clinical cure rates by pathogen for microbiologically evaluable patients including microbiologically evaluable patients with vancomycin-resistant Enterococcus faecium from the extension of this study.

Table 18. Cure Rates at the Test-of-Cure Visit for Intent-to-Treat, Modified Intent-to-Treat, and Clinically Evaluable Pediatric Patients for the Overall Population and by Select Baseline Diagnosis

Table 19. Cure Rates at the Test-of-Cure Visit for Microbiologically Evaluable Pediatric Patients with Infections due to Gram-positive Pathogens

REFERENCES

1. Clinical and Laboratory Standards Institute (CLSI). Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria that Grow Aerobically; Approved Standard – Tenth Edition. CLSI document M07-A10, Clinical and Laboratory Standards Institute, 950 West Valley Road, Suite 2500, Wayne, Pennsylvania 19087, USA, 2015.

2.Clinical and Laboratory Standards Institute (CLSI). Performance Standards for Antimicrobial Susceptibility Testing; Twenty-fifth Informational Supplement. CLSI document M100-S25, Clinical and Laboratory Standards Institute, 950 West Valley Road, Suite 2500, Wayne, Pennsylvania 19087, USA, 2015.

3.Clinical and Laboratory Standards Institute (CLSI). Performance Standards for Antimicrobial Disk Susceptibility Tests; Approved Standard – Twelfth Edition. CLSI document M02-A12, Clinical and Laboratory Standards Institute, 950 West Valley Road, Suite 2500, Wayne, Pennsylvania 19087, USA, 2015.

Medication Guide

PATIENT INFORMATION

Patients should be counseled that antibacterial drugs including ZYVOX should only be used to treat bacterial infections. They do not treat viral infections (e.g., the common cold). When ZYVOX is prescribed to treat a bacterial infection, patients should be told that although it is common to feel better early in the course of therapy, the medication should be taken exactly as directed. Skipping doses or not completing the full course of therapy may (1) decrease the effectiveness of the immediate treatment and (2) increase the likelihood that bacteria will develop resistance and will not be treatable by ZYVOX or other antibacterial drugs in the future.

Patients should be advised that:

· ZYVOX may be taken with or without food.

· They should inform their physician if they have a history of hypertension.

· Large quantities of foods or beverages with high tyramine content should be avoided while taking ZYVOX. Foods high in tyramine content include those that may have undergone protein changes by aging, fermentation, pickling, or smoking to improve flavor, such as aged cheeses ,fermented or air-dried meats ,sauerkraut , soy sauce, tap beers, and red wines. The tyramine content of any protein-rich food may be increased if stored for long periods or improperly refrigerated.

· They should inform their physician if taking medications containing pseudoephedrine HCl or phenylpropanolamine HCl, such as cold remedies and decongestants.

· They should inform their physician if taking serotonin re-uptake inhibitors or other antidepressants.

· Phenylketonurics: Each 5 mL of the 100 mg/5 mL ZYVOX for Oral Suspension contains 20 mg phenylalanine. The other ZYVOX formulations do not contain phenylalanine. Contact your physician or pharmacist.

· They should inform their physician if they experience changes in vision.

· They should inform their physician if they have a history of seizures.

· Diarrhea is a common problem caused by antibiotics, which usually ends when the antibiotic is discontinued. Sometimes after starting treatment with antibiotics, patients can develop watery and bloody stools (with or without stomach cramps and fever) even as late as two or more months after having taken the last dose of the antibiotic. If this occurs, patients should contact their physician as soon as possible.

· Inform patient, particularly those with diabetes mellitus that hypoglycemic reactions, such as diaphoresis and tremulousness, along with low blood glucose measurements may occur when treated with linezolid. If such reactions occur, patients should contact a physician or other health professional for proper treatment.

This product’s label may have been updated. For current full prescribing information, please visit www.pfizer.com.