Acute Pain Management in Patients on Opioid Replacement Therapy

Inclusion Criteria:

1. Males and females aged 18-60 years of age, inclusive.
2. Maintained on stable buprenorphine/naloxone (Suboxone®) dose for at least 30 days prior to screening, with total daily dose \>=4 mg and \<=24 mg (Patients may also be on Zubsolv ® equivalent doses \>=2.9 and \<=17.2 mg). Participant must agree to stay on this dose for duration of study participation.
3. Urine toxicology screen negative for drugs of abuse but positive for buprenorphine.
4. Willing and able to speak, read and understand English.
5. Able and willing to perform/tolerate QST. Persons who can tolerate cold pressor testing for 5 minutes will be disqualified.
6. Willing to abstain from analgesic medications (other than buprenorphine) for 24 hours prior to each session.
7. Written informed consent obtained from participant and ability for participant to comply with the requirements of the study.

Exclusion Criteria:

1. Current alcohol or sedative-hypnotic use disorder as assessed by the Mini International Neuropsychiatric Interview.
2. Presence of acute or chronic pain as determined by medical history and physical examination and score of 0 on pain VAS at the start of experimental sessions.
3. Medical or psychiatric condition known to influence QST (e.g. HIV, peripheral neuropathy, Schizophrenia, Raynaud's syndrome).
4. Women who are pregnant, breastfeeding, or planning on becoming pregnant during course of trial. Women must be using effective birth control and will receive pregnancy tests before each session.
5. Poor venous access as an IV catheter will be used for blood draws during sessions.
6. Past history of psychotic disorder (as assessed through MINI).
7. Uncontrolled hypertension or clinically significant ECG abnormality.
8. History of allergy or significant adverse reaction to hydromorphone or ketamine.
9. Significant contraindication to ketamine use (active psychosis, uncontrolled hypertension, past or current ketamine use disorder, cardiovascular disease, glaucoma, active pulmonary infection or disease).