Duration of efficacy increases with the repetition of botulinum toxin A injections in primary palmar hyperhidrosis: A study of 28 patients

Background: Intradermal injections of botulinum toxin are effective but transitory in primary palmar hyperhidrosis. These injections are repeated when the symptoms recur. We do not know how the duration of efficacy changes when injections are repeated. Objective: In this retrospective study, we aimed to investigate the change in the duration of efficacy of botulinum toxin A (Dysport, Ipsen, Boulogne-Billancourt, France) with the repetition of injections in patients with primary palmar hyperhidrosis. Methods: From May 2001 to April 2012, 28 patients were treated with a dose of 250 U of botulinum toxin A per palm. We compared the duration of efficacy of the first and last toxin injections. Results: The median duration of efficacy was 7 months for the first injection and 9.5 months for the last, the difference being statistically significant (P = .0002). Limitations: Study limitations include a relatively small number of patients treated at a single center and evaluated retrospectively. Conclusion: To our knowledge, this study is the first to report a significant increase in the duration of efficacy of botulinum toxin A injections with the repetition of injections in patients with primary palmar hyperhidrosis. The reasons for this effect may be linked to the mechanism of action of botulinum toxin, and may improve our understanding of its pharmacologic effects.