Cost Effectiveness of Adjunctive Quetiapine Fumarate Extended-Release Tablets with Mood Stabilizers in the Maintenance Treatment of Bipolar I Disorder

Abstract

Bipolar I disorder (BPD I) is a recurrent illness that affects 1% of the US population and constitutes a large economic burden. However, few studies have investigated the cost effectiveness of maintenance treatment options for BPD I. To determine the cost effectiveness of maintenance treatment with quetiapine fumarate extended-release (XR) tablets in combination with mood stabilizers (lithium or divalproex) in comparison with the following treatments: placebo in combination with lithium or divalproex; no maintenance treatment; lithium monotherapy; lamotrigine monotherapy; olanzapine monotherapy; and aripiprazole monotherapy. The analysis was conducted from the societal and payer perspectives in the US, using a Markov model. The model simulated a cohort of 1000 stabilized BPD I patients and estimated the quarterly risk in three health states: euthymia, mania and depression. Efficacy data were derived from two randomized, double-blind trials comparing quetiapine + lithium/divalproex with placebo + lithium/divalproex for up to 2 years, as well as other published literature. Resource data were extracted from published literature. Drug costs, hospitalizations and physician visits were among the direct costs. Indirect costs included absenteeism, and mortality rates included suicide. Benefits and costs were discounted at 3% and the price reference year was 2009. Endpoints included number of acute mood episodes, hospitalizations due to an acute mood event and costs per QALY. Probabilistic sensitivity analysis (PSA) was conducted to evaluate uncertainty in the model inputs. Treatment with quetiapine XR + lithium/divalproex was associated with reductions in acute mania (46%), acute depression (41%) and related hospitalizations (44%) compared with placebo + lithium/divalproex, and similar reductions in events were observed relative to lithium monotherapy. In the base-case analysis from the payer perspective, the discounted incremental cost per QALY for quetiapine XR + lithium/divalproex compared with placebo + lithium/divalproex was $US22 959, and compared with lithium monotherapy was $US100 235, while all other comparators were dominated. PSA showed these results to be robust to select assumptions. Quetiapine XR + lithium/divalproex may be a cost-effective maintenance treatment option for patients with BPD I.