OBJECTIVES: To compare healthcare costs among patients who continued therapy or switched antimuscarinic agents for overactive bladder (OAB). METHODS: Patients initiating antimuscarinic therapy from 1/1/2007-3/31/2012 diagnosed with OAB were identified from a large claims database of privately insured patients. Patients were required to have no antimuscarinic claims in the 12 months before their antimuscarinic initiation (baseline period), continuous coverage for ≥12 months before and after antimuscarinic initiation, and age 18-64 years. Based on claims in the 6 months after antimuscarinic initiation, patients who continued index antimuscarinic therapy were categorized as persisters (n=3,197), and patients with a claim for a non-index antimuscarinic agent (without a gap >60 days after the end of index antimuscarinic treatment) were categorized as switchers (n=828). The study index date was defined as the date of switching from index antimuscarinic for switchers and a randomly assigned date (matching the distribution of time from initiation to switching) for persisters. All-cause and OAB-related costs (i.e., reimbursements to providers for medical and pharmacy claims) in the month prior to and 6 months after the index date were compared using generalized linear models controlling for baseline characteristics and baseline costs. RESULTS: Persisters compared with switchers were older and had lower baseline costs. After controlling for baseline characteristics and costs, all-cause and OAB-related costs in both the month before and 6 months after the index date were significantly lower among persisters than switchers (1 month before: all-cause $1,222 vs. $1,759, OAB-related $142 vs. $170; 6 months after: all-cause $7,017 vs. $8,806, OAB-related $642 vs. $797; all p<0.0001). CONCLUSIONS: All-cause and OAB-related costs in the period immediately before and after switching were higher among patients who switched antimuscarinic therapies compared with patients who persisted on their index antimuscarinic therapy.