Duration of efficacy increases with the repetition of botulinum toxin A injections in primary axillary hyperhidrosis: a study in 83 patients.

BACKGROUND: Intradermal injections of botulinum toxin are effective but transitory in primary axillary hyperhidrosis. These injections are repeated when the symptoms recur. The reported duration of efficacy is variable, from 2 to 24 months, but it is unknown how the duration of efficacy changes when injections are repeated. OBJECTIVE: In this retrospective study, we aimed to evaluate changes in the duration of efficacy of botulinum toxin injections (Dysport, Ipsen, Boulogne-Billancourt, France) with the repetition of injections in patients with axillary hyperhidrosis. METHODS: From May 2001 to April 2012 inclusive, 83 patients were treated with a dose of 125 U per underarm. We compared the duration of effect of the first and last toxin injections. RESULTS: The median duration of efficacy for the first injection was 5.5 months, whereas that for the last injection was 8.5 months. The difference between these 2 durations is statistically significant (P = .0002). LIMITATIONS: Although retrospective and based on the declarative, this work is the first to our knowledge to highlight this benefit of treatment and to evaluate botulinum toxin over such a long period (11 years). CONCLUSION: There appears to be an increase in the duration of efficacy of botulinum toxin A injections with the repetition of injections in patients with primary axillary 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.