This study aims to find out how different doses of an investigational substance affect the body and mind. The information collected in this study may help researchers and regulatory agencies better understand the risks associated with opioid use in humans. Overall, this study is intended to provide important scientific information about certain kinds of opioids, including their potential for misuse, dependence, and other safety concerns.

You may be eligible for this study if you meet the following criteria.

Inclusion Criteria:

• Recreationally used opioids at least 10 times in the past year
• Recreationally used opioids at least once in the past 12 weeks
• No history of opioid use disorder diagnosis
• Live in Texas
• Ages 18-55
• Agree not to use any recreational drugs during study participation

Exclusion Criteria:

• Substance use disorders other than cannabis or tobacco use disorder
• History of overdose from opioids
• Currently seeking treatment for substance or alcohol use disorder
• Uncontrolled psychiatric conditions

If enrolled in this study, you will complete several study phases, including screening, qualification, treatment, and follow-up. Most study procedures will happen in person at the study site.

Screening

During screening, participants will complete procedures to determine eligibility, which may include:

• Questions about medical history, substance use history, physical and mental health
• Urine drug testing
• Pregnancy testing when applicable
• ECG
• Vital signs
• Bloodwork

Some screening activities or follow-up discussions may be completed by phone or virtually when appropriate, but key study visits must occur in person.

Qualification

If eligible, you will next complete a qualification phase, which includes an inpatient stay and a naloxone challenge to help determine whether you can safely continue in the study.

Treatment

During the treatment phase, you will attend multiple in-person study sessions where you will receive an investigational substance or a placebo. The study team will monitor you closely.

Follow-Up

Throughout your participation, the study team will collect information about how you feel, monitor you for side effects or adverse events, and complete follow-up assessments after the treatment phase is complete.

Compensation may be available if eligible. Transportation support may also be available.

There is no cost for you to participate in our research study.