[Preliminary report: the efficacy of clonidine hydrochloride ointment for postherpetic neuralgia]

The combination of clonidine hydrochloride, alpha 2-agonist, and opioid is useful for relieving the pain due to surgical procedures or cancer. The routes of administrations used are intravenous, intramuscular as well as intrathecal, epidural and transmucosal. However, transdermal clonidine has not been reported. We, therefore, investigated the analgesic effect of local administration of clonidine ointment. Ten patients with postherpetic neuralgia (PHN) were selected randomly. They were requested to fill out a questionnaire after applying clonidine ointment (150 micrograms/ointment 1 g) to the painful area. Items included in the questionnaire were: effectiveness, visual analog scale (VAS) before and after the administration of clonidine ointment, onset time, with or without allodynia and effectiveness to allodynia in the former case, side effects, and patients' background. Analysis of the answers indicates that clonidine ointment produced a satisfactory effect in nine patients. Onset time was within a few minutes in most patients. No patients suffered any side effects. Specific mechanism of effectiveness or the site affected has not been confirmed in this study, but considering the quick onset, it is presumed that the site where the ointment was applied was the very site that was affected. Clonidine hydrochloride ointment was effective in relieving the symptoms of PHN.