Cost-effectiveness to tolterodine for patients with urge incontinence who discontinue initial therapy with oxybutynin: A Canadian perspective

BACKGROUND: Tolterodine is a novel muscarinic receptor antagonist for the treatment of overactive bladder. OBJECTIVE: The purpose of this study was to examine the cost-effectiveness of tolterodine for patients with urge incontinence (UI) who discontinue initial therapy with oxybutynin in a Canadian setting. METHODS: We compared 2 treatment strategies for the management of adult patients with UI: (1) generic oxybutynin with no further treatment for patients who discontinue and (2) generic oxybutynin with switch to tolterodine (2 mg BID) for patients who discontinue. We developed a 1-year Markov model (4-week cycle length) with transitions between disease states of normal, mild, moderate, and severe. Transition probabilities over 12 weeks were obtained from randomized trial data, and drug discontinuation rates were obtained from Quebec prescription claims data. Outcome measures were time in "normal" health state and quality-adjusted life-years (QALYs) using EuroQol-5D utility scores from a survey of Swedish patients with overactive bladder. Costs to the health care payer and patient out-of-pocket costs (in Canadian dollars) were included. RESULTS: For patients who discontinue oxybutynin, the use of tolterodine is associated with approximately 6 months per year in a normal health or mild disease state, compared with approximately 3 months for those who do not receive further drug therapy after discontinuation. Tolterodine use resulted in an annual additional cost per patient of Can $163. The incremental cost per QALY was Can $9,982 and appeared to be robust to alternative model parameter assumptions. CONCLUSION: Use of tolterodine in patients with UI who discontinue initial therapy with generic oxybutynin lies within currently accepted benchmarks for cost-effectiveness.