| Title | Effect of Valproate on Olanzapine Plasma Concentrations in Patients With Bipolar or Schizoaffective Disorder. | | Author(s) | Spina E, Dʼarrigo C, Santoro V, Rosaria Muscatello M, Pandolfo G, Zoccali R, Diaz FJ, de Leon J | | Institution | From the Section of Pharmacology, Department of Clinical and Experimental Medicine and Pharmacology, University of Messina and IRCCS Centro Neurolesi "Bonino-Pulejo"; daggerDepartment of Neurosciences, Psychiatric and Anesthesiological Sciences, University of Messina, Messina, Italy; double daggerDepartment of Statistics, Universidad Nacional, Medellin, Colombia; and section signUK Mental Health Research Center at Eastern State Hospital, Lexington, KY. | | Source | Ther Drug Monit 2009 Oct 27. | | Abstract | The effect of valproate on the steady-state plasma concentrations of olanzapine was investigated in 18 patients with bipolar or schizoaffective disorder. Additional valproate, at a dose ranging from 600 to 2000 mg/d, was administered for 4 weeks to patients stabilized on olanzapine (5-20 mg/d). During valproate coadministration, mean plasma olanzapine concentrations decreased significantly from 32.9 +/- 9.7 ng/mL at baseline to 27.4 +/- 9.8 ng/mL at week 2 (P = 0.02), and to 26.9 +/- 9.2 ng/mL at week 4 (P = 0.001). Smoking also decreased plasma olanzapine concentrations. Valproate coadministration with olanzapine was well tolerated and no patient showed a worsening of his or her psychopathological condition. These findings indicate that valproate, at doses of up to 2000 mg/d, is associated with a minimal, presumably not clinically significant, decrease in plasma olanzapine concentrations, possibly as a result of induction of olanzapine metabolism. New studies are needed to confirm that valproate could have mild inductive effects. | | Language | ENG | | Pub Type(s) | JOURNAL ARTICLE
| | PubMed ID | 19865002 |
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