Marijuana Effect on Differentiating an Opioid from Placebo During the Discrimination Phase of a Human Abuse Potential Study

Subjects of human abuse potential (HAP) studies must be able to detect liking with the investigational drug. However, many subjects recruited for HAP studies use marijuana, and THC is often exempt from exclusion by urine drug tests (UDTs). PRA Health Sciences examined whether UDT evidence of recent marijuana use was associated with a difference in subjects’ ability to discriminate opioid from placebo. Successful opioid discriminators were associated with a statistically insignificant, but higher positive THC UDT rate and mean carboxy-THC urine concentration when compared to non-discriminators, indicating that recent users of marijuana may not need to be excluded from opioid HAP studies.