Pharmacokinetics and antipsychotic effect of remoxipride in chronic schizophrenic patients

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Abstract
Single dose pharmacokinetics and the antipsychotic effect of 4 weeks treatment with three fixed dose levels of remoxipride (a selective D2 receptor antagonist) were studied in chronic, stable schizophrenic inpatients. After a placebo washout of 1 month, 15 patients entered the study. Of these, 11 patients received a single 50 mg oral dose of remoxipride for pharmacokinetic evaluations. All 15 patients were randomly assigned to treatment with oral remoxipride either 25 mg t.i.d., 50 mg t.i.d. or 100 mg t.i.d. for 4 weeks. Blood samples for remoxipride and prolactin assays were taken at 0, 0.33, 0.5, 0.66, 1.0, 1.5, 2, 3, 4, 8, 12, 24, 28, 32 and 48 h after drug intake. The pharmacokinetic characteristics were similar to those previously found in normal healthy volunteers: the mean peak plasma concentration of remoxipride after 50 mg was 3.3 μmol/l, the mean time to reach this was 2.1 h; the mean area under the plasma concentration/time curve was 27.8 μmol/1.h.1 -1 and the mean elimination half-life of remoxipride was 5.5 h. A significant increase in prolactin levels was detected 2 h after administration of remoxipride but they had reverted to normal 8 h after drug intake in all but one patient. Antipsychotic effects were estimated using the brief psychiatric rating scale (BPRS) and the Krawiecka rating scale (KRS) at admission, baseline (end of the 4 week placebo washout period) and after 7, 14 and 28 days treatment. Following an increase in mean psychosis ratings for both positive and negative symptoms during the placebo washout period, these decreased during active treatment and at the end of the study were similar to the scores on admission. Thus the possible efficacy of remoxipride in chronic patients with negative symptoms should be further explored in placebo controlled studies. Remoxipride was well tolerated. Sleep disorders occurred in three patients, extrapyramidal symptoms were not aggravated and no clinically significant effects were observed on the cardiovascular system, in clinical chemistry or haematology.