Opioid Use Disorder (OUD)

Find out what they are actually on - Ask which maintenance drug (methadone, buprenorphine, buprenorphine/naloxone, or depot naltrexone), the dose, and when they last took it. That one answer decides whether your opioids will work at all.

Tolerance is pharmacology, not drug-seeking - Chronic mu stimulation means standard induction and maintenance doses under-treat. Titrate against a baseline that already includes their home requirement rather than an opioid-naive number.

Buprenorphine blocks your full agonists - It is a partial mu agonist with high receptor affinity and slow dissociation kinetics, so it occupies the receptor and prevents full agonists like fentanyl and morphine from binding. Its own analgesia has a ceiling. Build the plan around NSAIDs, regional anesthesia and nerve blocks, or anticonvulsants instead of escalating fentanyl into an occupied receptor.

Depot naltrexone leaves you no opioid at all - The 380 mg IM depot has a half-life of 5 to 10 days and antagonizes the mu receptor outright. Elective surgery inside that window needs a non-opioid plan; the block does not lift because you gave more fentanyl.

Never precipitate withdrawal on your watch - Abrupt cessation, or a dose of naloxone, buprenorphine, or naltrexone given to someone still opioid-dependent, sets it off. Patients on chronic opioids should be tapered, not stopped.

Titrate naloxone, don't slam it - In a known opioid-dependent patient with overdose symptoms, start at 0.04 to 0.1 mg IV and aim for respiratory drive, not full reversal. Full reversal buys you a combative, aggressive patient in acute withdrawal. Reserve 0.4 mg IV for patients with no known dependence, and 1 to 2 mg IV for apnea or cyanosis.

Watch them after reversal - Naloxone's half-life is 30 to 80 minutes, shorter than methadone, fentanyl, or buprenorphine. Monitor at least 6 to 12 hours after a reversal or the respiratory depression returns. Reversing a buprenorphine overdose specifically takes a 2 to 3 mg naloxone bolus followed by a 4 mg/hr infusion to overcome its receptor affinity.

Methadone and the QT - Rapid methadone dose escalation is associated with arrhythmias including QT prolongation. Get a baseline 12-lead ECG and read the QTc before stacking other QT-prolonging drugs.

Don't stack sedatives - Benzodiazepines enhance opioid effect and raise overdose risk. Buprenorphine plus diazepam specifically has produced respiratory and cardiovascular collapse.

Look for what travels with injection use - Hepatitis A, B, and C screening is positive in roughly 80% to 90% of injection opioid users, HIV rates reach 60% in some regions, and LFTs may be elevated from adulterants or resolving hepatitis. Inspect the arms for scars and needle marks before you go hunting for an IV, and keep endocarditis, osteomyelitis, cellulitis, and septic emboli on the differential.

Discharge is the dangerous window - Mortality peaks in the first four weeks of treatment and the four weeks after it ends, and over 90% relapse within a month of withdrawal. Send them out with a naloxone kit and a named follow-up.

Agent-specific detail lives elsewhere - This entry covers the shared pharmacology. Heroin Use Disorder, Methadone Maintenance Use, and Buprenorphine Maintenance Use carry the drug-by-drug specifics, and Opioid Withdrawal Syndrome carries the timeline and treatment.

Opioid use disorder (OUD) is continued opioid use despite social, professional, and medical harm. DSM-5 requires two or more of eleven problems within 12 months; six or more marks severe disease. Opioids act at mu, delta, and kappa G-protein-coupled receptors, and mu drives both the reinforcement and the respiratory depression. Chronic mu stimulation suppresses endogenous endorphin production and superactivates adenylyl cyclase, so the system runs against a counter-regulatory brake.

That adaptation is what you meet in the OR. Tolerance makes a normal induction dose look like placebo, and the same nervous system decompensates into withdrawal the moment the exogenous opioid is removed or displaced. Up to 50% of patients on chronic opioid therapy meet OUD criteria, and mortality on chronic opioids runs about ten times that of the general population.