Safety of botulinum toxin type A: a systematic review and meta-analysis

Objective: To define quantitatively the safety and tolerability profile of botulinum toxin type A (BTX-A) across all common therapeutic indications. The review was limited to the evaluation of the safety profile of one preparation of BTX-A (BOTOX*) because distinct formulations of BTX-A are associated with different clinical profiles, requiring separate consideration for an analysis of safety. Research design and methods: We identified randomized controlled trials of BTX-A through searches of the MEDLINE, EMBASE, and Cochrane Controlled Trial databases for the years 1966-2003. Studies were double-blind, randomized, crossover, or of parallel group design. The search strategy included the terms 'botulinum toxin', 'therapeutic use', 'randomized controlled trial', 'controlled clinical trial', 'randomized clinical trial', and 'placebo controlled trial'. Only randomized controlled trials of at least 7 days duration that reported adverse events were included in the analysis. Main outcome measure: Safety was assessed by means of a meta-analysis of the number and frequency of adverse events. Results: Thirty-six studies involving 2309 subjects met the inclusion criteria. These reported on 1425 subjects receiving BTX-A treatment. No study reported any severe adverse events. The meta-analysis of any mild to moderate adverse events showed a rate of roughly 25% in the BTX-A-treated group (353/1425 patients) compared with 15% in the control group (133/884 patients, p < 0.001). Focal weakness was the only adverse event that occurred significantly more often with BTX-A treatment than control. Conclusion: The results of this meta-analysis and experience from long-term, open-label investigations demonstrate that the formulation of BTX-A evaluated here has a favorable safety and tolerability profile across a broad spectrum of therapeutic uses.