Topical lidocaine gel relieves postherpetic neuralgia

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Abstract
Postherpetic neuralgia (PHN) following herpes zoster is a common and disabling neuropathic pain syndrome. In a double‐blind, three‐session study, 5% lidocaine gel or vehicle was applied simultaneously to both the area of pain and to the contralateral mirror‐image unaffected skin. In the local session, lidocaine gel was applied to the painful skin area. In the remote session, lidocaine gel was applied to mirror‐image skin. In the placebo session, vehicle was applied bilaterally. For cranial PHN, gel was applied without occlusion for 8 hours. For limb or torso PHN, gel was applied under occlusion for 24 hours. The 16 subjects with cranial PHN reported pain relief significantly favoring local drug application at 30 minutes, 2, 4, and 8 hours. The 23 subjects with torso or limb PHN reported significantly lower pain intensity with local drug application at 8 hours and both pain relief and reduced pain intensity at 24 hours. Remote lidocaine application to mirror‐image skin was no different from placebo. No systemic adverse effects were reported and blood levels did not exceed 0.6 μg/ml. Topical application of 5% lidocaine gel relieves PHN pain by a direct drug action on painful skin.