A Study to Assess the Pharmacokinetics, Safety, and Tolerability of Paliperidone Palmitate in Patients With Schizophrenia

This is a multicenter, randomized (the study drug is assigned by chance), open-label (all people know the identity of the intervention), parallel-group (each group of patients will be initiated simultaneously) study in 4 panels (A, B, C and D). Each panel will comprise 2 single-dose treatment periods. In Period 1, all patients from the 4 panels will receive an intramuscular (i.m.) injection with 1 mg paliperidone as an immediate release (IR) solution to assess tolerability and allergic or hypersensitivity reactions potentially related to paliperidone, and to establish the relative bioavailability (the extent to which a drug or other substance becomes available to the body) of paliperidone palmitate versus paliperidone IR. Patients in Panels A and C will receive an i.m. injection with 1 mg paliperidone IR solution in the gluteal muscle, and patients in Panel B and D will receive an i.m. injection with 1 mg paliperidone IR solution in the deltoid or gluteal muscle. Patients who tolerate this injection and have completed all assessments on Day 5 of Period 1 will be enrolled in Period 2. In Period 2, patients will receive a single dose of 3-month paliperidone palmitate i.m. injection at the dosages defined for each panel. The study drug injection will be followed by a 96-hour observation period in Period 1, and a 364-day or 544-day observation period in Period 2. Successive study drug administrations will be separated by a washout period (period when receiving no treatment) of at least 7 and no more than 21 days. The total study length for all patients is from 53 weeks to a maximum of 58 weeks. Patients in Panel B, if consented, and Panel D will participate in the extension period of approximately 26 weeks in order to obtain additional assessments to be able to characterize the pharmacokinetics (PK) profile. Pharmacokinetics explores how the drug is absorbed in the body, distributed within the body, and how it is removed from the body over time. Therefore, for those who participate in the extension period, the total study duration will be approximately 84 weeks.