Dose Ranging Study in Healthy Methadone Maintenance Subjects

A Randomized, Double-blind, 4-period Crossover, Dose-ranging Study to Determine the Effects on the Oral-cecal Transit Time of Single Doses of MOA-728 and the Safety and Tolerability of Multiple Doses of MOA-728 in Stable Methadone Maintenance Subjects

To assess the effect of a single oral dose of MOA-728, an investigational drug, on the oral-cecal transit time in subjects who are taking methadone.

1. Men or nonlactating and nonpregnant women, aged 18 to 65 years
2. Healthy as determined by the investigator on the basis of medical history, physical examination, clinical laboratory test results, vital signs, and 12-lead electrocardiogram