A Pharmacokinetic and Safety Study of Risperidone Long Acting Injectable in Schizophrenic Patients

• The max and min plasma concentrations, average plasma concentration, and time to reach the max plasma concentration at steady-state (2 weeks after 6th dose). Safety data for all timepoints will be summarized.
  

• The change at Week 12 from the baseline of the total score, positive symptom score, negative symptom score, total psychiatric score and BPRS scores from the PANSS.
  

This is an open-label, multicenter, randomized, 3-arm trial to compare the pharmacokinetic profile and the safety profile between 3 dose groups. There are 2 periods in this study: a 10-week treatment period and an 8-week follow-up period. Patients will receive 6 injections of long acting injectable risperidone at one of the dose levels (25, 37.5 and 50 mg) every 2 weeks according to their randomly assigned treatment. Blood samples will be collected throughout the 10-week treatment and 8-week follow-up period to determine the changes in study drug concentration in the plasma. Safety will be assessed by monitoring of adverse events, subjective symptoms/objective findings, laboratory tests, physical examinations, electrocardiograms, injection site reactions, and the Drug-Induced Extrapyramidal Symptoms Scale (DIEPSS). Efficacy of the study drug will be assessed based on the Positive and Negative Syndrome Scale (PANSS) and the Clinical Global Impression - Severity (CGI-S) and Clinical Global Impression - Change (CGI-C) scales. The patients will receive injections of long acting injectable risperidone (either 25, 37.5, or 50 mg) in their muscle every 2 weeks for 10 weeks for a total of 6 injections.