Inclusion Criteria:  Adults with chronic pain. Age greater than or equal to 18 years on the day of enrolment. Subjects are currently taking a daily opioid pain medication and planning to taper the dose. Participants complete at least one voluntary opioid dose reduction in the twelve-week study period. Glomerular filtration rate (GFR) > 50 mL/min Capable of providing informed consent  Exclusion Criteria:  Allergy to probenecid or related drugs History of uric acid renal calculi, if known to be urate calculi. If unknown type, then any history of renal calculi. Known G6PD deficiency Active gout in any joint  Current use of drugs whose exposure may be prolonged, or risk of toxicity increased when used in combination with probenecid:  Penicillins, specifically ampicillin, penicillin G sodium, and piperacillin Carbapenems, specifically doripenem and meropenem Lorazepam, midazolam, nitrazepam Ketorolac Oseltamivir Methotrexate Mycophenolate  Current use of drugs which may mask symptoms of withdrawal:  a. Clonidine, lofexidine, tizanidine  Current use of drugs which may diminish the effect of probenecid:  a. High dose salicylates including greater than 325 mg PO daily of acetylsalicylic acid (ASA)  Pregnancy or breastfeeding Any major comorbid medical condition which might impair follow-up or result in a safety risk to the participant  Participation in another clinical trial investigating a drug, medical device, or a medical procedure during the 30 days prior to enrolment.  -