Therapeutic advantages of monitoring plasma concentrations of perphenazine in clinical practice.

Two hundred and twenty-eight acute paranoid psychotic in-patients received continuous treatment with perphenazine for a period of at least 5 weeks, before blood samples were taken to determine perphenazine plasma levels and conclusions regarding therapeutic efficacy and motor side effects. Patients with plasma concentrations within the range of 2-6 nmol/l showed an excellent antipsychotic response, concomitantly with a low incidence of extrapyramidal side effects. However, patients with plasma levels below or above this range either demonstrated a poor therapeutic response or a high degree of side effects respectively. The results indicate that with increasing age significantly lower doses of perphenazine are required to ensure an optimal clinical response. No difference, however, was seen between sexes with regard to dose response.