After completing the screening process, participants will be scheduled for admission onto the General Clinical Research Unit on 5-South for a 13-week study. During Week 1, participants will be detoxified from opioids. During Week 2 after the detoxification period, participants will be randomized to receive one of four maintenance doses of NT-814. During Weeks 3-4 participants may receive oxycodone during laboratory sessions and will complete a cue exposure session involving presentation of neutral and drug cues. Participants then will have the opportunity to self-administer drug by making clicks on a computer mouse. Weeks 2, 5, 8, and 11 will be medication stabilization weeks following by testing during Weeks 3-4, 6-7, 9-10, and 12-13. At the conclusion of the study, participants will be given an exit interview during which the study will be described. Those who are interested in treatment for their drug use at the end of the study will be offered referrals to studies at our Substance Treatment and Research Service or other treatment providers.