A Study of the Potential Effects of Trimethoprim on the Pharmacokinetics of ER OROS Paliperidone

This study was designed as a single center, open-label, randomized, 2 treatment period crossover study in healthy male volunteers. The study consists of a screening period (within 21 days before the first study drug administration) before randomization; an open-label treatment phase consisting of 2 periods during which subjects will receive a single oral dose of ER OROS paliperidone alone (Treatment A) or in combination with 200 mg trimethoprim twice daily (Treatment B); and end-of-study evaluations upon completion of all the study procedures in Period 2 or early withdrawal. The pharmacokinetic blood and urine samples will be collected over a 96 hour period after ER OROS paliperidone administration. Successive ER OROS paliperidone administrations will be separated by at least 14 days. Given that the main elimination route of paliperidone is renal clearance and about half of this is through active secretion in the renal tubule, competition for this route of elimination can occur when other actively secreted drugs are coadministered. Therefore, the possible influence on the renal excretion of paliperidone will be investigated when a competitor for active renal secretion, trimethoprim, is coadministered. Safety and tolerability will be monitored throughout the study. Treatment A: a single oral dose of 6 mg ER OROS paliperidone on Day 1; Treatment B: a 200 mg trimethoprim tablet twice daily from Day 1 to Day 8 and a single oral dose of 6 mg ER OROS paliperidone on Day 5.