- Substance abuse, such as alcohol (greater than or equal to 80 gm/day), IV drugs and inhaled drugs. If the subject has a history of substance abuse, to be considered for inclusion into the protocol, the subject must have abstained from using the abused substance for at least 12 months. Stable subjects enrolled in a methadone maintenance program for at least one year may be enrolled if they are otherwise eligible and are monitored throughout the study for illicit drug use.