- Subject is a recreational opioid user who is NOT physically dependent on opioids based on Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition-Text Revision (DSM-IV-TR) criteria, and the Naloxone Challenge. A recreational opioid user is defined as recreationally abusing opioids for non-therapeutic purposes (i.e., for psychoactive effects) on at least 10 occasions within the last year and at least once in the 12 weeks prior to Visit 1.