Laboratory for Experimental Cutaneous Pain and Itch Research, SMI, Center for Neuroplasticity and Pain, Department of Health Science and Technology, Faculty of Medicine, Aalborg University, Denmark.
Laboratory for Experimental Cutaneous Pain and Itch Research, SMI, Center for Neuroplasticity and Pain, Department of Health Science and Technology, Faculty of Medicine, Aalborg University, Denmark.
J Pain. 2021 Jul;22(7):778-788. doi: 10.1016/j.jpain.2021.01.005. Epub 2021 Jan 30.
To prevent pain associated with 8% capsaicin application, pretreatment with local anesthetics, such as EMLA (eutectic mixture of lidocaine 2.5% and prilocaine 2.5%), is considered an option. However, there is contradicting evidence regarding the effects of local analgesia on capsaicin-induced desensitization. In session 1, 2 skin areas in each forearm of 24 healthy volunteers were randomized to 2-hour pretreatment with EMLA/placebo cream. After pretreatment, 8% capsaicin patches were applied for 3 hours in 1 placebo and 1 EMLA pretreated area, obtaining the following four areas: Capsaicin + EMLA, Capsaicin + Placebo, EMLA alone, and Placebo. Pain intensity scores were assessed during the 3-hour application of capsaicin. Warmth detection, heat pain sensitivity, and microvascular reactivity were measured after the removal of capsaicin. After 24 hours, in session 2, all tests were repeated followed by histamine application in each area to examine itch intensity and neurogenic flare. Overall, EMLA caused significant reductions in capsaicin-induced pain compared with placebo (P= .007) and enhanced the capsaicin-induced increase in superficial blood perfusion immediately after the 3-hour capsaicin application (P< .01). Regardless of pretreatment, capsaicin induced heat hyperalgesia immediately after the application (P< .001). Twenty-four hours post application, heat pain sensitivity was normalized. However, WDT increased significantly (P< .001). Capsaicin tended to reduce the itch intensity and significantly reduced the neurogenic flare (P< .05) induced by histamine compared with EMLA alone. The findings suggest that pretreatment with topical analgesic cream reduces application site pain without interfering with the 8% topical capsaicin-induced desensitization. PERSPECTIVE: Pretreatment with local anesthetic EMLA cream might be considered a good therapeutic option to reduce the pain associated with 8% capsaicin application currently used for treatment of neuropathic pain syndromes. This study also suggests the existence of a synergistic effect of capsaicin and EMLA on the process of neurogenic inflammation.
为了预防 8%辣椒素应用引起的疼痛，可以考虑使用局部麻醉剂（如 EMLA，即 2.5%利多卡因和 2.5%丙胺卡因的混合物）进行预处理。然而，关于局部镇痛对辣椒素诱导脱敏的影响存在相互矛盾的证据。在第 1 次治疗中，24 名健康志愿者的每只前臂随机分为 2 个区域，分别接受 2 小时 EMLA/安慰剂乳膏预处理。预处理后，在 1 个安慰剂和 1 个 EMLA 预处理区域贴敷 8%辣椒素贴片 3 小时，共获得以下 4 个区域：辣椒素+EMLA、辣椒素+安慰剂、EMLA 单独应用和安慰剂。在应用 3 小时辣椒素的过程中评估疼痛强度评分。在去除辣椒素后测量温暖感、热痛觉和微血管反应性。24 小时后，在第 2 次治疗中，在每个区域中重复所有测试，然后应用组胺以检查瘙痒强度和神经源性 flare。总体而言，与安慰剂相比，EMLA 显著降低了辣椒素引起的疼痛（P=.007），并在 3 小时辣椒素应用后立即增强了辣椒素诱导的浅层血液灌注增加（P<.01）。无论是否进行预处理，辣椒素在应用后立即引起热痛觉过敏（P<.001）。应用后 24 小时，热痛觉敏感性恢复正常。然而，WDT 显著增加（P<.001）。与 EMLA 单独应用相比，辣椒素倾向于降低组胺诱导的瘙痒强度，并显著降低神经源性 flare（P<.05）。这些发现表明，局部镇痛乳膏预处理可减轻应用部位疼痛，而不干扰 8%局部辣椒素诱导的脱敏作用。观点：局部麻醉剂 EMLA 乳膏预处理可能被认为是减轻目前用于治疗神经病理性疼痛综合征的 8%辣椒素应用相关疼痛的良好治疗选择。本研究还表明，辣椒素和 EMLA 对神经源性炎症过程具有协同作用。
