Cost-effectiveness analysis of extended-release formulations of oxybutynin and tolterodine for the management of urge incontinence

INTRODUCTION: Oxybutynin and tolterodine are two drugs widely used for the management of overactive bladder and urge urinary incontinence. The once-daily, extended-release formulations benefit from being well tolerated and efficacious. However, their costs, compared with generic immediate-release (IR) oxybutynin, are significantly greater. This study compared the cost effectiveness of oxybutynin extended-release (Oxy-XL), tolterodine extended-release (Tol-ER), tolterodine immediate-release (Tol-IR) and oxybutynin immediate-release (Oxy-IR).

STUDY DESIGN: A cost-effectiveness model.

METHODS: A systematic review that identified appropriate randomised clinical trials provided evidence on efficacy. Empirical models of drug effects (number of incontinent-free weeks) and persistence (proportion of patients still on therapy) were constructed in order to determine clinical effectiveness which was combined with cost data (direct medical costs to the UK NHS, year 2001 values) to calculate the drugs' cost-effectiveness from the perspective of the NHS. Univariate sensitivity analyses were conducted to test the robustness of the results.

PATIENTS: Hypothetical cohort of patients with urge incontinence associated with overactive bladder.

MAIN OUTCOME MEASURES AND RESULTS: The incremental cost per incontinent-free week for Oxy-IR (versus no treatment) ranged from pound sterling 2.58 to pound sterling 16.59. Oxy-XL and Tol-ER were more effective than Oxy-IR but at additional costs per incontinent-free week. Tol-IR did not appear to be a cost-effective option as it was less effective and more costly than the extended-release formulations. Uncertainty surrounding the health and cost consequences of early discontinuation affected these results, although the model results were robust to parameter uncertainty.

CONCLUSION: Oxy-IR, Oxy-XL and Tol-ER appear to be cost-effective options for the management of urge incontinence from the NHS perspective. A decision among the treatments depends on the acceptable cost per additional incontinent-free week.