• Opioid agonist effects (measured by Visual Analog Scale and Adjective Rating Scale during the medication challenge sessions)
  
• Physiological effects (measured by pulse oximeter, blood pressure, heart rate, and pupillary camera during the medication challenge sessions)
  

Opioid withdrawal symptoms are a major contributing factor for why opioid treatment programs often fail. Individuals with severe opioid withdrawal may experience shaking, muscle and bone pain, nausea, depression, anxiety, and drug craving. Buprenorphine, a medication that is used to treat opioid addiction, works by lessening the withdrawal symptoms. However, past research has shown that individuals who use buprenorphine are at risk for abusing the drug. Naloxone, another medication, is currently used to treat substance addiction. It is also used in combination with buprenorphine to reduce the risk of buprenorphine abuse in individuals who are physically dependent upon opioids. The purpose of this study is to compare the abuse potential of buprenorphine versus a buprenorphine and naloxone combination in non-dependent opioid users.

This 7-week study will enroll non-dependent opioid users. Participants will take part in two medication challenge sessions per week. At each challenge session, participants will be randomly assigned to receive varying doses of either buprenorphine; a buprenorphine and naloxone combination; hydromorphone, which is a medication used to treat moderate to severe pain; or placebo. Buprenorphine and naloxone will be administered as tablets that are dissolved under the tongue. Hydromorphone will be injected. During the challenge sessions, participants will complete performance tasks to measure psychomotor and cognitive functioning. Questionnaires and self-reports will be completed to assess medication effects. Heart rate and blood pressure will be monitored throughout all sessions, and a specialized camera will be used to assess pupillary response of the eyes.