Acta Dermato-Venereologica 99-13CompleteContent

CLINICAL REPORT 1237 Duration of Efficacy Increases with the Repetition of Botulinum Toxin A Injections in Primary Axillary Hyperhidrosis: A 15-year Study in 117 Patients Clémence BERTHIN and Hervé MAILLARD Department of Dermatology, Le Mans Hospital, Le Mans, France Changes in the duration of efficacy of botulinum toxin A injections for primary axillary hyperhidrosis have not been studied in depth. The aim of this study was to assess such changes. In a retrospective cohort of 220 patients, seen over a 17-year period, duration of efficacy was recorded, including duration of efficacy of first and last injections. Of 220 patients, 117 fulfil led the study criteria (79 females and 38 males, age 17–79 years, mean age 38.3 years). Patients received 3–24 injections (mean 5.5). The duration of efficacy of the first injections was 3 weeks to 30 months (median 6 months), and the duration of efficacy of the final in jections was 3 weeks to 66 months (median 8 months) (p < 0.001). An increase in duration of efficacy occur red in 62% of patients with repeated injections. Of the 20 patients with a follow up ≥10 years, the mean number of treatments was 8.25/patient; in 18 of these patients the duration of efficacy increased by > 50%. In conclusion, repeated botulinum toxin A injections lead to an increase in duration of efficacy without se condary decrease. Key words: hyperhidrosis; botulinum toxin; duration of efficacy. Accepted Aug 26, 2019; E-published Aug 27, 2019 Acta Derm Venereol 2019; 99: 1237–1240. Corr: Hervé Maillard, Department of Dermatology, Le Mans Hospital, 194 Avenue Rubillard, FR-72037 Le Mans Cedex, France. E-mail: hmaillard@ ch-lemans.fr S weating is a physiological mechanism of thermoregu- lation. Hyperhidrosis consists of excessive sweating, which can negatively affect quality of life (1–3). The reported prevalence varied from 4.8% in the USA (4) to 14.5% in Shanghai, China, in 2016 (5). Primary focal hyperhidrosis is defined by excess swea- ting for more than 6 months without any apparent cause that fulfils at least 2 of the following criteria: onset of symptoms during childhood or adolescence (< 25 years), occurrence of sweating independent of temperature, unforeseeably and not consciously controllable, focal oc- currence in one or more sites of predilection with bilateral symmetry, occurrence of more than once a week that in- terferes with daily activities, absence of night sweats, and family history of the disease (6). The exact underlying mechanism is poorly understood, but it is thought to be linked to an important genetic disorder: Higashimoto et al. (7) showed a family history of hyperhidrosis in 42% SIGNIFICANCE Hyperhidrosis consists of excessive sweating, which can negatively affect quality of life. Primary axillary hyperhi- drosis is one of the most frequent causes of hyperhidro- sis. Its treatment requires frequently repeated injections of botulinum toxin A (BTA). There are few published data on the repetition of BTA injections and its consequences. We report here a significant increase in the efficacy dura- tion with the repetition of injections after more than 15 years of BTA treatment: 80% of patients reported a stable or increasing efficacy duration at the end of the follow-up, without side-effects. of 456 patients with primary hyperhidrosis and found predisposing loci on chromosome 14q11.2-q13. Several treatments are currently available, but they are not curative. A recent study on hyperhidrosis treatment (6) codified the therapeutic escalation. Topical therapy, such as aluminium chloride antiperspirants, should be the first line of treatment. In the second intention, several treatments can be proposed: iontophoresis, oral medica- tion, or injection of botulinum toxin A (BTA). Another way to control hyperhidrosis is to destroy the sudoral glands using microwaves, called Miradry ® , after local anaesthesia (8). Finally, the last treatment consists of thoracic sympathectomy by endoscopy for upper limb hyperhidrosis. BTA is a neurotoxin that is produced by the bacterium Clostridium botulinum. Treatment with BTA injections works by irreversibly blocking the release of the neuro transmitter acetylcholine from presynaptic bulbs at the neuromuscular junction (9). This leads to degeneration of the nerve endings, which can redevelop in a few weeks. This mechanism explains the temporary efficacy of this treatment from 4 to 25 months (10). Several studies have shown that the duration of the effect increases with the number of injections (10, 11). Conversely, other studies have suggested that this treatment can lead to the production of antitoxin antibodies in some patients (12). There are several suspected risk factors: a short duration between 2 series of BTA injections (less than 4 months), higher doses of BTA if the optimal efficiency is not reached, and a high cumulative dose (13). There are few published studies on changes in the duration of the efficacy (DE) of BTA injections over time and favouring factors (14). This is an open access article under the CC BY-NC license. www.medicaljournals.se/acta Journal Compilation © 2019 Acta Dermato-Venereologica. doi: 10.2340/00015555-3307 Acta Derm Venereol 2019; 99: 1237–1240

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