Muscatello, Maria R. A. and Pacetti, Monica and Cacciola, Massimo and La Torre, Diletta and Zoccali, Rocco A. and D'Arrigo, Concetta and Migliardi, Gaetana and Spina, Edoardo (2005) Plasma Concentrations of Risperidone and Olanzapine during
Coadministration with Oxcarbazepine. Epilepsia, 46 (5). pp. 771-774. ISSN 0013-9580
Purpose: Oxcarbazepine (OZC) is a secondgeneration
antiepileptic drug (AED) that also may be used as
a mood stabilizer. Unlike carbamazepine (CBZ), which is an
inducer of the cytochrome P-450 isoforms and may accelerate
the elimination of several therapeutic agents, OXC seems
to have only a modest inducing action. The aim of this investigation was to evaluate the effect of a treatment with OXC on plasma concentrations of the new antipsychotics risperidone and olanzapine.
Methods: OXC, at a dosage of 900Â–1,200 mg/day, was administered for 5 consecutive weeks to 25 outpatients, 10 men and 15 women, aged 25 to 64 years, with bipolar or schizoaffective disorder. Twelve patients were stabilized on risperidone therapy (2Â–6 mg/day) and 13 on olanzapine (5Â–20 mg/day). Steady-state plasma concentrations of risperidone and its active metabolite 9-hydroxyrisperidone (9-OH-risperidone) and olanzapine were
measured by high-pressure liquid chromatography (HPLC) before addition of OXC and after 5 weeks from the start of adjunctive treatment.
Results:OXC caused only minimal and no significant changes
in the mean plasma levels of risperidone (from 5.6Â±3.6 ng/ml at baseline to 4.8 Â± 2.6 ng/ml at week 5), 9-OH-risperidone (from 23.6Â±7.5 to 24.7Â±7.4 ng/ml), and olanzapine (from 26.5Â±5.7 ng/ml at baseline to 27.8 Â± 5.1 ng/ml). OXC coadministration with either risperidone or olanzapine was well tolerated.
Conclusions: Our findings indicate that OXC does not affect
the elimination of risperidone and olanzapine, thus confirming its weak inducing effect on hepatic drug-metabolizing
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