Botulinum toxin a in postherpetic neuralgia: A parallel, randomized, double-blind, single-dose, placebo-controlled trial

Objectives: Cumulative evidence support a beneficial effect of botulinum toxin A (BTX-A) in postherpetic neuralgia (PHN). We aimed to assess efficacy, safety, and tolerability of BTX-A in the management of PHN, performing a randomized, double-blind, single-dose, placebo-controlled trial. Methods: Thirty adults with PHN were randomized either to BTXA or placebo. Severity of pain was evaluated by patients using a visual analogue scale (VAS) and quality of sleep was assessed using a 5-item questionnaire. Primary outcome was reduction in VAS score, with a greater than 50% reduction being considered clinically significant. Secondary outcomes were reduction in sleep score and maintenance of VAS score after treatment, with over 50% maintenance considered clinically meaningful. Results: Thirteen patients from the experimental arm achieved an at least 50% reduction in VAS score, compared with none of the placebo patients (NNT=1.2, 95% CI, 2-1; ARR=0.87, 95% CI, 055-096; P