Repetitive injections of botulinum toxin A continuously increase the duration of efficacy in primary axillary hyperhidrosis: a retrospective analysis in 101 patients.

BACKGROUND AND OBJECTIVES: Botulinum toxin type A is an effective, well-tolerated, albeit temporary treatment for primary axillary hyperhidrosis. However, little is known about the influence of repetitive injections on the duration of efficacy. PATIENTS AND METHODS: 139 patients with primary axillary hyperhidrosis were injected with 50 units of botulinum toxin per axilla. In 101 patients, who received at least three treatments, the duration of efficacy after the first, second, and last treatment was evaluated. RESULTS: The median duration of efficacy was 4.0 months, 4.5 months, and 5.0 months after the first, second, and last injection, respectively. Overall, the duration of efficacy was significantly longer after the last injection compared to the duration of efficacy after the first injection (p = 0.0055, Wilcoxon matched-pairs signed-rank test). Likewise, the difference between the first and second injection (p = 0.0302) as well as the difference between the second and the last injection (p = 0.0381) were significant. In 25.7 % of patients, the duration of efficacy remained unchanged over the entire treatment period. CONCLUSIONS: Repetitive botulinum toxin treatments led to a significantly increased duration of efficacy in axillary hyperhidrosis. While the average duration of efficacy continued to increase with each treatment, there were considerable interindividual differences.