Tolerability of solifenacin and oxybutynin immediate release in older (>65 years) and younger (≤65 years) patients with overactive bladder: sub-analysis from a Canadian, randomized, double-blind study

Overactive bladder (OAB) is a common condition whose prevalence increases with age. Antimuscarinic agents are the pharmacologic treatment of choice, but adverse events such as dry mouth may lead to early discontinuation. The purpose of this analysis was to compare the incidence and severity of dry mouth and other adverse events with solifenacin 5 mg/day and oxybutynin immediate release (IR) 15 mg/day in patients 65 years and > 65 years in the Canadian VECTOR study (VEsicare in Comparison To Oxybutynin for oveRactive bladder patients). VECTOR was a randomized, multicentre, prospective, double-blind, double-dummy study in 132 subjects with epsilon 1 urgency episode per 24 h, with or without urgency incontinence, and epsilon 8 micturitions per 24 h for epsilon 3 months. After a 2-week washout, patients received solifenacin 5 mg once daily or oxybutynin IR 5 mg tid for 8 weeks. For the current post-hoc analysis, adverse events were evaluated in subgroups of patients 65 years and > 65 years, using a full logistic regression model, multinomial logit regression model and reduced model. NCT00431041. The incidence and severity of dry mouth and other adverse events with solifenacin were similar between younger and older patients. In both age subgroups, solifenacin 5 mg/day was associated with fewer episodes and lower severity of dry mouth, and a lower discontinuation rate, compared with oxybutynin IR 15 mg/day. Solifenacin 5 mg/day was better tolerated than oxybutynin IR 15 mg/day in younger (65 years) and older (> 65 years) subgroups. Solifenacin was equally well tolerated in both age subgroups. Limitations of the analysis were that the study was not preplanned to perform post-hoc subgroup analysis, patients knew that dry mouth was a primary outcome, and the study used fixed doses of each drug.