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.
Effect of valproate on olanzapine plasma concentrations in patients with bipolar or schizoaffective disorder
SPINA, Edoardo;MUSCATELLO, Maria Rosaria Anna;PANDOLFO, Gianluca;ZOCCALI, Rocco Antonio;
2009-01-01
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.Pubblicazioni consigliate
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