 12. The subject has a positive pre-study drug screen. A minimum list of drugs that will be screened for includes amphetamines, barbiturates, cocaine, opiates, cannabinoids, phencyclidine PCP and benzodiazepines. Subjects with CHC may be included if they have a positive result for cannabinoids at screening. However, they must be willing to abstain from cannabinoid use throughout the duration of the study. 