Short-Term Effects of 10% Lidocaine Ointment on Allodynia in Cancer Pain: A Randomized, Double-Blind, Placebo-Controlled Crossover Study.

Abstract

<b><i>Background:</i></b> There is currently no established therapy for allodynia, which is a type of neuropathic pain. However, high concentrations of topical anesthetics can anesthetize the skin and increase the sensory threshold to tactile stimulation. <b><i>Objective:</i></b> We aimed to evaluate the short-term effects and safety of 10% lidocaine ointment for treating allodynia in cancer pain. <b><i>Design:</i></b> This was a randomized double-blind crossover study comparing the efficacies of 10% lidocaine ointment and placebo ointment for the treatment of static allodynia and spontaneous pain within 24 hours after ointment application, using a numerical rating scale (NRS). <b><i>Setting/Subjects:</i></b> The subjects were 25 cancer patients with current pain rating of ≥4 on NRS of static allodynia in cancer pain. <b><i>Results:</i></b> The NRS scores for static allodynia were significantly lower in the lidocaine group than in the placebo group at two to eight hours after initial ointment application. A total of 56% of patients (95% confidence interval 35%-77%) had NRS improvements of ≥50% at eight hours after lidocaine ointment application compared with 20% (3%-37%) after placebo ointment application. There was no interaction between time and group in terms of NRS values for spontaneous pain (<i>p</i> = 0.835), but a significant main effect of group was found, with NRS scores being significantly lower in the lidocaine group than in the placebo group (<i>p</i> = 0.027). There were no adverse events associated with lidocaine use. <b><i>Conclusions:</i></b> Lidocaine ointment 10% can alleviate allodynia for two to eight hours after application.