A Randomized, Open-label, 3-period Crossover Study to Determine the Relative Bioavailability of Two Oral Formulations of MOA-728 and to Compare the Pharmacodynamics of the Two Oral Formulations of MOA-728 and the Subcutaneous Formulation in Subjects on Stable Methadone Maintenance

Primary: To determine the relative bioavailability of MOA-728, an investigational drug, administered orally in both the capsule and tablet formulations to methadone maintenance subjects.Secondary: To assess the pharmacodynamic effect of MOA-728 administered both orally and subcutaneously to methadone maintenance subjects using the oral-cecal transit time.