Effects of Ibudilast on Oxycodone Self-administration in Opioid Abusers

Opioid drugs increase glial cell activation which may be related to the abuse liability of opioid drugs. Data supporting this hypothesis have demonstrated that glial cell attenuators decrease the positive rewarding aspect of opioids in laboratory animals. Ibudilast (MN-166, formerly AV411) is a compound that inhibits the activation of glia. Recent preclinical studies demonstrate that while ibudilast increases the analgesic effects of opioids, it decreases the rewarding effects of such drugs. It has also been shown that ibudilast suppresses morphine-induced release of dopamine, a primary neurotransmitter involved in the rewarding and reinforcing effects of abused drugs. Additionally, we recently found that ibudilast decreases subjective symptoms of opioid withdrawal in opioid dependent humans during detoxification. Therefore, the primary aim of this 6-7 week inpatient study is to investigate the ability of MN-166 to dose-dependently alter the reinforcing, analgesic, subjective, performance, and physiological effects of oxycodone, a commonly abused prescription opioid. This study includes a 10-day morphine taper phase, followed by two study phases (approximately 18 days each) with daily active ibudilast and placebo administration, respectively. After the detoxification phase, participants are randomized to receive placebo or MN-166, and then be stabilized on the medication. Thereafter, participants will complete laboratory sessions. Subsequently, during Phase 2, participants will cross over to the other treatment arm, stabilize, and complete laboratory sessions.