Background: Switching to another antidepressant is one of the alternative treatment strategies employed in major depressive disorder (MDD) patients who have no remission despite an adequate trial of an antidepressant. The aim of the present study was to present an economic evaluation of sertraline compared with venlafaxine after unsuccessful treatment for depression with citalopram.
Material and Method: An economic model was constructed in line with the design of the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) study. MDD patients who did not have a remission with or who had an intolerance to citalopram were randomly assigned to be switched to either sertraline or venlafaxine. Patients who had no remission at the end of the switching treatment phase still continued the antidepressants and received an adjunctive treatment with aripiprazole. The event probabilities were used to derive the transitional probabilities use in the model. The primary model outcome was remission of symptoms and the secondary outcome was quality-adjusted life years (QALYs). Incremental cost-effectiveness ratios (ICEs) were estimated for the costs per unit of effectiveness. Sensitivity analyses were done to assess the effects of model assumptions.
Results: The total direct costs per remission were 27,830 Baht for sertraline and 30,147 Baht for venlafaxine. Sertraline had lower total costs per QALY than venlafaxine (34,788 Baht vs. 37,683 Baht). The more cost-effectiveness of sertraline resulted in 7.68% of cost saving. The incremental cost of venlafaxine compared with sertraline was 2,316 Baht per remission gained and 2,895 Baht per QALY gained. By varying the remission rate of venlafaxine from 20% to 40%, the sensitivity analysis results in a decrease in total costs of venlafaxine from 31,926 Baht to 24,808 Baht. In addition, incremental cost per remission gained changed from 4,096 Baht in favour of sertraline to 3,023 Baht in favour of venlafaxine. Similarly, incremental cost per QALY gained changed from in favour of sertraline to in favour of venlafaxine.
Conclusion: Based on the STAR*D trial, the results of the economic study indicate that a switch to sertraline is a costeffectiveness treatment option compared with a switch to venlafaxine in MDD patients who have no remission or cannot tolerate citalopram.

Keywords: Cost-effectiveness, Sertraline, Venlafaxine, Switching, Major depressive disorder