LACK OF EFFECT OF AMITRIPTYLINE ON RISPERIDONE PHARMACOKINETICS IN SCHIZOPHRENIC-PATIENTS

The interaction between plasma concentrations of the tricyclic antidep ressant amitriptyline and the metabolism of the new antipsychotic risp eridone was studied in 12 patients with chronic schizophrenia. Each pa tient received 3 mg risperidone twice a day for 28 days. Amitriptyline was coadministered at doses of 50 mg/day on day 15 and 100 mg/day on days 16 to 21. Amitriptyline did not significantly affect the mean pla sma concentrations or pharmacokinetics of risperidone in schizophrenic patients or influence the antipsychotic fraction (the total concentra tion of risperidone and 9-hydroxyrisperidone, its primary and biologic ally active metabolite). These results suggest that risperidone dose n eed not be adjusted when coadministered with amitriptyline at doses up to 100 mg/day in schizophrenic patients.