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CARN-AP: Psychopharmacology and Medication Management

CARN-AP · Work through your exam, one topic at a time.

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Psychopharmacology and Medication Management

Core knowledge

Three FDA-approved medications treat opioid use disorder: methadone (full agonist, dispensed through federally regulated opioid treatment programs), buprenorphine (partial agonist with a ceiling effect on respiratory depression), and naltrexone (antagonist). Buprenorphine induction requires a COWS score of roughly 8-12 and adequate abstinence from short-acting opioids (typically 12-24 hours) to prevent precipitated withdrawal. Naltrexone requires 7-10 days opioid-free and baseline liver function tests. Alcohol use disorder has three approved agents: naltrexone (oral or long-acting injectable, reduces heavy drinking), acamprosate (supports abstinence; renally cleared, dose-adjusted in impairment), and disulfiram (aversive deterrent requiring supervision and 12-24 hours of abstinence before the first dose). Off-label options include topiramate and gabapentin. Tobacco treatment includes varenicline, bupropion, and nicotine replacement. Alcohol withdrawal is managed with benzodiazepines titrated to a symptom scale; opioid withdrawal is managed symptomatically with alpha-2 agonists, antiemetics, and antidiarrheals. Naloxone co-prescribing is expected practice for anyone on long-term opioids or at overdose risk.

Traps

  • Starting buprenorphine too early causes precipitated withdrawal; starting naltrexone too early causes acute withdrawal and receptor blockade.
  • Buprenorphine plus a benzodiazepine warrants caution and monitoring, not automatic refusal of care.
  • Methadone prolongs QTc and interacts with CYP3A4 inhibitors and inducers; both are heavily tested.
  • Disulfiram reactions occur with hidden alcohol: mouthwash, hand sanitizer, cough syrup, and some sauces.

Rule of thumb

Before starting, match the drug to the baseline test: naltrexone, liver function tests; acamprosate, renal function; methadone, ECG and QTc. Worked example: a patient on methadone 110 mg has a QTc of 510 ms. Hold or reduce the dose, repeat the ECG, correct potassium and magnesium, and avoid other QT-prolonging agents.