Prolactin Levels After Switching to Paliperidone Palmitate in Patients with Schizophrenia

Objective: The aim of this study was to investigate the tolerability and efficacy of paliperidone palmitate and its effect on the levels of prolactin in patients with schizophrenia. Method: A prospective study was carried out in 22 Japanese middle-aged patients with schizophrenia who were switched from paliperidone-extended release or risperidone long-acting injectable to paliperidone palmitate for a minimum of 12 months. Psychotic symptoms using the 18-item Brief Psychiatric Rating Scale, extrapyramidal symptoms using 9-item Drug-induced Extrapyramidal Symptoms Scale, and plasma prolactin levels using fasting blood samples were assessed at Baseline, and one, three, six, and 12 months. Results: There were significant reductions in prolactin levels at one, three, and six months relative to baseline in the male subjects switched from risperidone long-acting injectable, while prolactin levels in male subjects switched from paliperidone-extended release and the female subjects switched from risperidone long-acting injectable or paliperidone-extended release were largely unchanged. No time-sequential changes were observed in total scores of Brief Psychiatric Rating Scale and Drug-induced Extrapyramidal Symptoms Scale, irrespective of previous antipsychotics treatment. Conclusion: Switching from paliperidone-extended release or risperidone long-acting injectable to paliperidone palmitate did not result in any observed time-sequential changes in psychotic symptoms in study subjects, and prolactin levels decreased in male subjects switched from risperidone long-acting injectable. As measurement of paliperidone concentrations is limited in routine practice, a fluctuation range of prolactin levels may be a useful marker for confirmation of safety maintenance treatment with long-acting injectables in clinical settings.