Canadian economic comparison of extended-release oxybutynin and immediate-release tolterodine in the treatment of overactive bladder.

BACKGROUND: Overactive bladder (OAB) is a condition characterized by urgency, increased frequency of micturition, or urge incontinence. It affects a considerable segment of the population, particularly with increasing age. Pharmacotherapy is one of the most common approaches to the treatment of OAB.

OBJECTIVE: This article describes the development and results of a model comparing health-economic outcomes for the new extended-release (XL) formulation of oxybutynin and immediate-release (IR) tolterodine in a population of community-dwelling Canadian adults with OAB.

METHODS: A Markov model was developed to compare health-economic outcomes over the course of 1 year. Effectiveness and treatment-persistence data were derived from the OBJECT (Overactive Bladder: Judging Effective Control and Treatment) trial, a 3-month comparison of oxybutynin XL 10 mg and tolterodine IR 4 mg, and were used, together with data from the literature (identified through a MEDLINE search of articles published between 1990 and 2003), to project outcomes beyond the trial period. Severity-specific cost profiles for incontinence were developed. In the principal analyses, cost items were limited to drug therapy, physician visits, use of pads or other protection, and laundry costs. Costs are reported in 2002 Canadian dollars.

RESULTS: Costs after 1 year were estimated to be an average of $32 less per patient for oxybutynin XL compared with tolterodine IR, and 3.1 additional patients in every 100 who received oxybutynin XL were expected to attain complete continence compared with those who received tolterodine. During the course of 1 year, patients receiving oxybutynin XL were expected to have a mean 16.5 additional incontinence-free days compared with those receiving tolterodine IR. The results were sensitive to relative drug prices. In the other sensitivity analyses, however, oxybutyrin XL maintained its advantage over a wide range of inputs.

CONCLUSION: The results of these analyses suggest that when priced equivalently, oxybutynin XL would reduce costs and provide better results than tolterodine IR over 1 year of treatment.