Economic impact of extended-release tolterodine versus immediate- and extended-release oxybutynin among commercially insured persons with overactive bladder

Objective: To examine levels of persistence and compliance as well as the economic impact of extended-re I ease tolterodine (tolterodine ER) versus immediate- and extended-release oxybutynin (oxybutynin IR or oxybutynin ER) among commercially-insured patients with overactive bladder (OAB). Methods: Patients with OAB who initiated tolterodine ER, oxybutynin IR, or oxybutynin ER between January 2001 and December 2002 were identified from the PharMetrics Patient-Centric database; the first medication used in this timeframe was used for treatment group assignment (ie, patients were only in I group). Exploratory assessment of persistency and compliance was conducted among all treated patients: subjects were matched 1:1 based on the estimated propensity score for tolterodine ER in remaining analyses. Measures included patient characteristics as well as levels of medication, outpatient and inpatient resource utilization, and costs. Primary comparisons were made descriptively; costs were evaluated using generalized linear models with a gamma distribution and log-link function. Results: Compliance did not differ between tolterodine ER (77.4%) and oxybutynin ER (74.3%), but was lower for oxybutynin IR (60.9%). Mean (+/- standard deviation) duration of therapy was higher for tolterodine ER (139 +/- 132 days) versus oxybutynin ER (115 +/- 122) and oxybutynin IR (60 +/- 85). Totals of 7257 and 5936 matched pairs were available for tolterodine ER versus oxybutynin ER and oxybutynin IR comparisons, respectively. The mean age was 54 years in all groups; the majority was women. Utilization of outpatient and inpatient medical services was consistently lower among tolterodine ER patients in both comparisons. Total costs were slightly lower for tolterodine ER versus oxybutynin ER ($8303 +/- $18802 vs $8862 +/- $18684) and oxybutynin IR ($9975 +/- $24860 vs $10521 +/- $22602); differences were significant after multivariate adjustment. Conclusions: Use of tolterodine ER results in comparable compliance to oxybutynin ER and longer duration of use relative to either form of oxybutynin. In addition, tolterodine ER may be cost-effective relative to oxybutynin IR or oxybutynin ER among commercially-insured persons with OAB.