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


CONCLUSIONS
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.


CONCLUSIONS
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.
Astellas Pharma Europe Ltd , Chertsey, Surrey , UK.
J
J
Nazir
W M
WM
Hart
D001561:Benzilates / Q000191:economics* / Q000627:therapeutic use; D003362:Cost-Benefit Analysis; D004305:Dose-Response Relationship, Drug; D005858:Germany; D006296:Health Services / Q000191:economics / Q000706:statistics & numerical data; D006801:Humans; D018803:Models, Economic; D009313:National Health Programs; D009662:Nortropanes / Q000191:economics* / Q000627:therapeutic use; D019057:Quality-Adjusted Life Years; D011812:Quinuclidines / Q000191:economics* / Q000627:therapeutic use; D000069464:Solifenacin Succinate; D044005:Tetrahydroisoquinolines / Q000191:economics* / Q000627:therapeutic use; D006113:United Kingdom; D053201:Urinary Bladder, Overactive / Q000188:drug therapy*; D064804:Urological Agents / Q000191:economics* / Q000627:therapeutic use; D016903:Drug Monitoring
D001561:Benzilates; D009662:Nortropanes; D011812:Quinuclidines; D044005:Tetrahydroisoquinolines; D064804:Urological Agents; C003330:trospium chloride; D000069464:Solifenacin Succinate
Cost; Overactive bladder; Solifenacin succinate; Trospium chloride; Utility