Lidocaine patch for therapy of neuropathic and non-neuropathic pain. A clinical case series of 87 patients

Background. Topical lidocaine patches (LP) reduce pain in postherpetic neuralgia and other forms of focal neuropathy. The aim of this study was to determine clinical predictors of therapeutic success. Material and methods. The medical histories of 87 patients with neuropathic (NS) and non-neuropathic pain (NNS) who had received LP as an add-on to their established pain medication were retrospectively analyzed. The variables assessed were gender, age, analgesic co-medication, pain localization, adverse effects and presence of dynamic allodynia. The impact of these variables on the clinical pain-relieving effect (scored on a 5-point scale) was investigated. Results. A total of 24 out of 28 patients with manifest allodynia scored the therapy with LP as beneficial, patients without allodynia (n=59, 67.8%) profited significantly less frequently with only 39% (p<0.001). The probability of profiting from LP therapy in the presence of allodynia was found to be about tenfold higher compared to patients without allodynia (odds ratio 9.14). Of the 87 patients investigated 48 were female (55.2%). Allodynia was considerably more frequent in women (39.6%) compared to men (23.1%) but this was insignificant. Of the female patients 62.5% responded to LP treatment, compared to only 43.6% of men. In more than 60% of cases rated as very good pain relief allodynia was manifest and in non-responders only in less than 10%. The variables age, pain localization and analgesic co-medication were not related with the success of therapy. Discussion. Patients with manifest allodynia profited significantly more frequently from LP therapy and were less frequently non-responders. Female patients showed therapeutic success more often together with a higher rate of allodynia. Conclusions. In the presence of allodynia, in especially of neuropathic origin, LP seems to be an effective and save option for add-on therapy, this being independent from pain localization and age. Gender specific effects however need more systematic investigation.