Long-term evaluation of the safety and efficacy of a novel 20% oxybutynin hydrochloride lotion for primary palmar hyperhidrosis: An open-label extension study.

The long-term safety and efficacy of 52-week application of oxybutynin hydrochloride 20% lotion (20% OL) for the treatment of primary palmar hyperhidrosis (PPHH) in Japanese patients aged ≥12 years were evaluated in an open-label extension (OLE) of a 4-week, randomized, double-blind (DB) study. The OLE included 114 patients who completed the DB study and wished to continue treatment and 12 new patients. In the safety analysis population (125 patients), the incidence of adverse events (AEs) and adverse drug reactions (ADRs) was 79.2% and 36.0%, respectively. Serious AEs were observed in two patients but were considered unrelated to the investigational drug. The incidence of AEs that led to study discontinuation was 1.6%. The incidence of application site AEs and ADRs was 35.2% and 26.4%, respectively. The severity of most events was mild. The incidence of anticholinergic AEs related to dry mouth was 3.2% for thirst and 0.8% for dry throat. The long-term efficacy of 20% OL was confirmed by a long-lasting reduction in sweat volume and improvement in the Hyperhidrosis Disease Severity Scale and Dermatology Life Quality Index. This study has several limitations: First the results may include some bias because most of the participants were from the prior DB study; second, the results may not be generalizable because only a few participants were in the age group most susceptible to PPHH (i.e., < 15 years old); and third, the study did not obtain safety information from treatment for more than 52 weeks, so this information must be collected in clinical practice in the future. No reduced therapeutic effect was observed in patients with PPHH in this study after 52-week application of 20% OL. Also, few patients experienced serious AEs or AEs that led to study treatment discontinuation.