Peripheral Neuropathy Unit, Imperial College London, Hammersmith Hospital, Area A, Ground Floor, Du Cane Road, London W12 ONN, UK.
Br J Anaesth. 2011 Oct;107(4):490-502. doi: 10.1093/bja/aer260. Epub 2011 Aug 17.
Topical capsaicin formulations are used for pain management. Safety and modest efficacy of low-concentration capsaicin formulations, which require repeated daily self-administration, are supported by meta-analyses of numerous studies. A high-concentration capsaicin 8% patch (Qutenza™) was recently approved in the EU and USA. A single 60-min application in patients with neuropathic pain produced effective pain relief for up to 12 weeks. Advantages of the high-concentration capsaicin patch include longer duration of effect, patient compliance, and low risk for systemic effects or drug-drug interactions. The mechanism of action of topical capsaicin has been ascribed to depletion of substance P. However, experimental and clinical studies show that depletion of substance P from nociceptors is only a correlate of capsaicin treatment and has little, if any, causative role in pain relief. Rather, topical capsaicin acts in the skin to attenuate cutaneous hypersensitivity and reduce pain by a process best described as 'defunctionalization' of nociceptor fibres. Defunctionalization is due to a number of effects that include temporary loss of membrane potential, inability to transport neurotrophic factors leading to altered phenotype, and reversible retraction of epidermal and dermal nerve fibre terminals. Peripheral neuropathic hypersensitivity is mediated by diverse mechanisms, including altered expression of the capsaicin receptor TRPV1 or other key ion channels in affected or intact adjacent peripheral nociceptive nerve fibres, aberrant re-innervation, and collateral sprouting, all of which are defunctionalized by topical capsaicin. Evidence suggests that the utility of topical capsaicin may extend beyond painful peripheral neuropathies.
局部辣椒素制剂用于疼痛管理。多项研究的荟萃分析支持低浓度辣椒素制剂的安全性和适度疗效，这些制剂需要每日重复自我给药。高浓度辣椒素 8%贴片（Qutenza™）最近在欧盟和美国获得批准。在患有神经病理性疼痛的患者中单次应用 60 分钟即可产生长达 12 周的有效止痛效果。高浓度辣椒素贴片的优点包括作用持续时间更长、患者依从性更好、发生全身作用或药物相互作用的风险较低。局部辣椒素的作用机制归因于 P 物质的耗竭。然而，实验和临床研究表明，伤害感受器中 P 物质的耗竭仅是辣椒素治疗的相关因素，对缓解疼痛几乎没有因果作用。相反，局部辣椒素在皮肤中起作用，通过一种最好被描述为“失功能化”伤害感受器纤维的过程来减轻皮肤过敏和减轻疼痛。失功能化是由于多种效应引起的，包括膜电位的暂时丧失、无法运输神经营养因子导致表型改变，以及表皮和真皮神经纤维末梢的可逆回缩。周围神经病理性过敏是由多种机制介导的，包括受影响或完整相邻周围伤害性神经纤维中辣椒素受体 TRPV1 或其他关键离子通道的表达改变、异常再神经支配和侧支发芽，所有这些都被局部辣椒素失功能化。有证据表明，局部辣椒素的应用可能不仅限于疼痛性周围神经病变。
