Examining Mu Opioid Mechanisms of Ketamine's Rapid Effects in OCD (MKET2)

Eligibility Criteria for Participants with OCD:

Inclusion Criteria:

   - Ages 18-65

   - Meet the criteria for OCD diagnosis

   - Failed at least 1 prior trial of standard first-line OCD treatment

   - Agree to the following lifestyle modifications: comply with requirements for fasting
   prior to the Experimental Session, not enroll in any other interventional clinical
   trials during the duration of the study, and commit to medication study procedures.

   - Able to provide informed consent

Exclusion Criteria:

   - prior naltrexone or ketamine use/exposure

   - Any current or past medical/psychiatric condition that makes participation unsafe in
   the opinion of the investigator or study physician

   - Pregnant or nursing, or able to become pregnant and are not practicing an effective
   means of birth control

   - the presence of metal in the body that is contraindicated for MRI scans

Eligibility Criteria for Healthy Volunteers:

Inclusion Criteria:

   - Ages 18-65

   - Able to provide informed consent

Exclusion Criteria:

   - current or past use of psychotropic medication

   - pregnant or nursing females

   - the presence of metal in the body that is contraindicated for MRI scans