The cost-effectiveness of solifenacin vs. trospium in the treatment of patients with overactive bladder in the German National Health Service

Abstract

Objective:

To carry out a cost–utility analysis comparing initial treatment of patients with overactive bladder (OAB) with solifenacin 5 mg/day versus either trospium 20 mg twice a day or trospium 60 mg/day from the perspective of the German National Health Service.

Methods:

A decision analytic model with a 3 month cycle was developed to follow a cohort of OAB patients treated with either solifenacin or trospium during a 1 year period. Costs and utilities were accumulated as patients transitioned through the four cycles in the model. Some of the solifenacin patients were titrated from 5 mg to 10 mg/day at 3 months. Utility values were obtained from the published literature and pad use was based on a US resource utilization study. Adherence rates for individual treatments were derived from a United Kingdom general practitioner database review. The change in the mean number of urgency urinary incontinence episodes/day from after 12 weeks was the main outcome measure. Baseline effectiveness values for solifenacin and trospium were calculated using the Poisson distribution. Patients who failed second-line therapy were referred to a specialist visit. Results were expressed in terms of incremental cost–utility ratios.

Results:

Total annual costs for solifenacin, trospium 20 mg and trospium 60 mg were €970.01, €860.05 and €875.05 respectively. Drug use represented 43%, 28% and 29% of total costs and pad use varied between 45% and 57%. Differences between cumulative utilities were small but favored solifenacin (0.6857 vs. 0.6802 to 0.6800). The baseline incremental cost–effectiveness ratio ranged from €16,657 to €19,893 per QALY.

Limitations:

The difference in cumulative utility favoring solifenacin was small (0.0055–0.0057 QALYs). A small absolute change in the cumulative utilities can have a marked impact on the overall incremental cost-effectiveness ratios (ICERs) and care should be taken when interpreting the results.

Conclusion:

Solifenacin would appear to be cost-effective with an ICER of no more than €20,000/QALY. However, small differences in utility between the alternatives means that the results are sensitive to adjustments in the values of the assigned utilities, effectiveness and discontinuation rates.

Keywords::

• Cost
• Overactive bladder
• Solifenacin succinate
• Trospium chloride
• Utility

Transparency

Declaration of funding

EcoStat Consulting UK Ltd was financed by Astellas Pharma Europe Ltd (APEL) to undertake this study.

Declaration of financial/other relationships

W.M.H. has disclosed that he is an employee of EcoStat Consulting UK Ltd. J.N. has disclosed that he is an employee of Astellas Pharma Europe Ltd.

JME peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Acknowledgments

We would like to thank Professor Axel Olaf Kern (University of Ravensberg) for providing the unit costs used in the analysis.