As Study of the Pharmacokinetics of Paliperidone Extended-release and Risperidone Immediate-release Formulations

This is an open-label, multiple-dose, parallel-group study in patients with schizophrenia or schizoaffective disorder. The study consists of a screening period (2 weeks maximum); a 1-week run-in or washout (Days 1 to 7) during which patients taking risperidone prestudy and randomly assigned to paliperidone treatment will receive replacement antipsychotic therapy, and other patients continue to take their prestudy antipsychotic medication; a 14-day open-label treatment period (Days 8 to 21); and a 5-day follow-up period. On Day 1 of the washout period, eligible patients will be randomized to receive ER OROS paliperidone (PAL) or risperidone (RIS). All patients will receive their first dose of study medication on Day 8 after randomization as follows: Patients randomized to PAL will receive 9 mg of ER OROS paliperidone daily from Day 8 to Day 14, followed by 15 mg of ER OROS paliperidone q.d. from Day 15 to Day 21. Patients randomized to RIS will receive dose-escalation up to 7 mg risperidone twice daily (b.i.d.) from Day 8 to Day 14, followed by 8 mg risperidone b.i.d. from Day 15 to Day 21. The study medication on Days 14 and 21 in the PAL group and on Day 21 in the RIS group will be administered after completion of a standardized high fat, high caloric breakfast. Patients will be confined to the testing facility from the morning of Day 8 (or earlier at the discretion of the investigator) until completion of the study procedures on Day 23. On all other assessment days, patients will return to the testing facility and remain there for the duration of the assessments.The highest dose of paliperidone currently being studied is 12 mg given as 6 tablets of 2 mg ER OROS paliperidone. In the currently proposed study, data on the safety and tolerability of the 15-mg dose will be monitored and collected. Paliperidone ER oral administration of 9 mg q.d. on Day 8 to 14, and 15 mg daily on Day 15 to 21; oral administration of escalating doses up to 7 mg risperidone twice daily (b.i.d.) between Days 8 and 14, inclusive, and 8 mg risperidone b.i.d. on Day 15 to 21