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Open-label steady-state pharmacokinetic drug interaction study on co-administered quetiapine fumarate and divalproex sodium in patients with schizophrenia, schizoaffective disorder, or bipolar disorder.

Winter HR, DeVane CL, Figueroa C, Ennis DJ, Hamer-Maansson JE, Davis PC, Smith MA

AstraZeneca Pharmaceuticals LP, Wilmington, DE, USA. helen.winter@astrazeneca.com

OBJECTIVE: To determine whether there is a pharmacokinetic drug interaction between quetiapine fumarate and divalproex sodium. METHODS: The pharmacokinetics and short-term tolerability and safety of coadministered quetiapine and divalproex were examined in adults with schizophrenia/schizoaffective disorder (Cohort A) or bipolar disorder (Cohort B) in an open-label, parallel, 2-cohort drug-interaction study conducted at three centers in the United States. Cohort A was administered quetiapine (150 mg bid) prospectively for 13 days, with divalproex (500 mg bid) added on days 6-13. Cohort B was administered divalproex (500 mg bid) for 16 days, with quetiapine (150 mg bid) added on days 9-16. Quetiapine and valproic acid plasma concentration-time data over a 12-h steady-state dosing interval were used to determine C(max), T(max), C(min), area under the plasma concentration-time curve (AUC(tau)), and oral clearance (CL/F). RESULTS: In Cohort A (n = 18), addition of divalproex did increase the C(max) of quetiapine by 17% but did not change AUC(tau). In Cohort B (n = 15), addition of quetiapine decreased both total valproic acid C(max) and AUC(tau) by 11%. No differences were observed in adverse events (AEs) with either quetiapine or divalproex monotherapy or their combination. CONCLUSION: Combination therapy with quetiapine (150 mg bid) and divalproex (500 mg bid) resulted in small and statistically non-significant pharmacokinetic changes.

Published 1 October 2007 in Hum Psychopharmacol, 22(7): 469-76.
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