Long-term treatment of chronic schizophrenia with risperidone: A study with plasma levels

Twenty-four chronic schizophrenic outpatients with a mean age of 37.21 years ± 9.96 SD were treated with risperidone (RSP) at the dosage of 2-9 mg/die (mean 4.46 mg/die ±1.30 SD, mean 0.06 mg/kg ± 0.01 SD) for a year. Clinical evaluation was assessed with the Brief Psychiatric Rating Scale(BPRs), Positive and Negative Symptoms scale (PANSS), Extrapyramidal Side Effects Rating Scale (EPSE) and a checklist for Anticholinergic Side Effects (ACS) at TO, then after 1 (T1), 2 (T2), 3 (T3), 6 (T6), 9 (T9) and 12 (T12) months. RSP and 9-hydroxy-risperidone (90H-RSP) plasma levels were determined at T12 by the HPLC method. BPRS and PANSS mean values showed a significant improvement during the study. No correlation between RSP dosage (mg/kg) and RSP, 90H-RSP plasma levels Or active moiety resulted. A positive correlation between age and active moiety was Observed. A positive correlation between RSP and 90H-RSP plasma levels was observed. A curvilinear relationship between active moiety and PANSS improvement (%) was observed. Patients with the higher PANSS amelioration showed RSP + 90H-RSP plasma levels ranging from 15 to 30 ng/mL. RSP seems to be quite an effective drug. It Seems, however, difficult to devise appropriate dose schedules and plasma level determination seems to be necessary in some cases,