The cost-effectiveness of aripiprazole as adjunctive therapy in major depressive disorder: Thai economic model.
BACKGROUND
Aripiprazole is the first atypical antipsychotic approved for adjunctive treatment to antidepressant therapy in patients with major depressive disorder (MDD). The current study aims to present an economic model and cost-effectiveness estimates for aripiprazole compared with placebo as adjunctive therapy to antidepressant treatment in patients with MDD who showed an incomplete response to a prospective 8-week trial of antidepressant therapy.


MATERIAL AND METHOD
An economic model of MDD treatment was developed to estimate the clinical and economic outcomes in Thai patients. Efficacy data were derived from a pooled analysis of two studies. A cost-effectiveness analysis was constructed in simulate the impact of treatment outcomes and costs over a 6-week time horizon. The primary outcome of the model was remission of symptoms. Quality-adjusted life-year (QALYs) was the secondary outcome. The event probabilities were used to derive the transitional probability used in the model and to calculate the weighted cost of each treatment outcome. Only direct costs were considered. One-way sensitivity analysis was performed to test the sensitivity of the model outputs.


RESULTS
Treatment with aripiprazole came at the total costs per remission of 30,970 Baht while treatment with placebo came at the total costs per remission of 28,409 Baht. Placebo had lower total costs per QALY than aripiprazole (35,511 Baht vs. 38,713 Baht). The incremental cost-effectiveness ratio (ICER) of augmentation with aripiprazole compared with placebo was 2,561 Baht per remission gained and 3,201 Baht per QALY gained. Aripiprazole dominated placebo if the value of transitional probability of remission changed to a value of greater than 0.348 from the base-case value of 0.257. Aripiprazole was more cost-effective than placebo as adjunctive therapy if the unit cost of aripiprazole is more than 48.9% discount.


CONCLUSIONS
Adjunctive aripiprazole is not more cost-effective than adjunctive placebo in Thai patients with MDD who showed an inadequate response to at least one prospective antidepressant therapy. Remission rates and unit cost are the key parameters involving the cost-effectiveness of aripiprazole.