Treatment of overactive bladder: a model comparing extended-release formulations of tolterodine and oxybutynin

The objective of this study was to compare 1-year total healthcare costs for patients with overactive bladder (OAB) initiating treatment with extended-release formulations of tolterodine and oxybutynin: tolterodine tartrate extended-release capsules (tolterodine ER) versus extended-release oxybutynin chloride (oxybutynin ER).

A model was developed from the payer perspective using data from the PharMetrics Patient-Centric database. Monthly discontinuation rates were derived from a cohort of newly treated patients with OAB (tolterodine ER, n = 15 394 or oxybutynin ER, n = 7934). All were assumed to be receiving therapy for at least 1 month. Medical management costs were based on reimbursement for all services for a matched cohort of patients taking tolterodine ER and oxybutynin ER. Medical management costs for those discontinuing therapy were based on patients receiving OAB care without pharmacotherapy (n = 29 992). Drug costs were from AnalySource (December 2004).

After the 11-month follow-up period, 21% of patients taking tolterodine ER and 15% of patients taking oxybutynin ER remained on original therapy. One-year average total costs per patient for those started on tolterodine ER were dollar 8876 and dollar 9080 for oxybutynin ER, a difference of dollar 204 per year. Sensitivity analyses indicated results were robust to changes in drug cost and probability of discontinuation. When discontinuation rates were held equal, cost differences continued to favor tolterodine ER (21%, dollar 272/yr; 15%, dollar 233/yr).

Those taking tolterodine ER had lower monthly drug and medical management costs. This resulted in a total average annual cost savings of dollar 204 per patient for those started on tolterodine ER. At the end of 1 year, patients with OAB were more likely to remain on original drug treatment taking tolterodine ER versus oxybutynin ER.