Tolerance of oral oxybutynin in the treatment of hyperhidrosis.

Oral oxybutynin (OOx) is an effective and safe treatment for the treatment of hyperhidrosis (HH). However, in some patients a loss of efficacy during prolonged treatment has been observed. Analysis of these cases could enable us to identify patients susceptible to OOx tolerance. An alternative treatment might then be considered. To assess tolerance to OOx in the treatment of HH. Secondarily, to assess epidemiological data and the duration of efficacy, together with the probable causes of any loss in this respect. Retrospective study of patients who started treatment with OOx for HH during the period 2007 to 2017 and who either abandoned this treatment due to loss of efficacy or needed higher daily doses to maintain the initial efficacy. Epidemiological data were collected, the duration of the efficacy of OOx was recorded and the possible causes of loss of efficacy were considered. The development of tolerance was suspected in 18 patients (8.5%) of the 211 who had previously responded to OOx. Thirteen patients abandoned OOx due to its lack of efficacy and five had to increase the dose in order to maintain efficacy. In seven patients, tolerance to the drug appeared in the first year of treatment, while in the remaining 11, the tolerance appeared later. Most patients achieved and maintained good control of HH with long-term OOx. However, in some cases the efficacy of the drug decreases. The study analysis did not produce findings enabling us to predict a loss of treatment efficacy.