4.4 Substance Use Disorders & Psychopharmacology
Key Takeaways
- Alcohol Withdrawal Syndrome progresses from autonomic hyperactivity (6–24 hours) to withdrawal seizures (12–48 hours), alcoholic hallucinosis (12–48 hours with intact sensorium), and Delirium Tremens (48–96 hours; 5% mortality), treated acutely with symptom-triggered benzodiazepines (CIWA-Ar protocol).
- Pharmacotherapy for Alcohol Use Disorder includes naltrexone (first-line mu-opioid antagonist; contraindicated in active opioid use or liver failure), acamprosate (NMDA modulator; safe in liver disease, dose-adjusted in renal impairment), and disulfiram (aldehyde dehydrogenase inhibitor).
- Opioid overdose presents with the classic triad of respiratory depression, miosis (pinpoint pupils), and central nervous system depression, treated immediately with intravenous or intranasal naloxone.
- Lithium toxicity presents with coarse tremor, ataxia, confusion, and nephrogenic diabetes insipidus when serum levels exceed 1.5 mEq/L; hemodialysis is indicated for levels >2.5 mEq/L with severe symptoms or >4.0 mEq/L regardless of symptoms.
- Neuroleptic Malignant Syndrome (NMS) presents with hyperthermia, 'lead-pipe' muscle rigidity, autonomic instability, and elevated creatine kinase (CK), requiring drug discontinuation, supportive care, and dantrolene or bromocriptine.
Pathophysiology & DSM-5 Diagnostic Framework for Substance Use Disorders
Substance use disorders (SUD) are characterized by a cluster of cognitive, behavioral, and physiological symptoms indicating that the individual continues using the substance despite significant substance-related problems. Diagnosis under DSM-5 requires meeting ≥2 of 11 criteria over a 12-month period across four domains: impaired control, social impairment, risky use, and pharmacological criteria (tolerance and withdrawal).
Alcohol Use Disorder: Acute Withdrawal & Delirium Tremens Protocol
Alcohol chronic use enhances inhibitory GABA neurotransmission and downregulates NMDA glutamate receptors. Abrupt cessation leads to uninhibited CNS excitation due to GABA hypofunction and NMDA hyperactivation.
Alcohol Withdrawal Timeline & CIWA-Ar Protocol
- Mild Autonomic Tremors / Agitation (6–24 hours post-last drink): Tremor, diaphoresis, tachycardia, hypertension, anxiety, insomnia, nausea.
- Withdrawal Seizures (12–48 hours): Generalized tonic-clonic seizures, usually single or brief bursts.
- Alcoholic Hallucinosis (12–48 hours): Visual, auditory, or tactile hallucinations with intact sensorium and normal vital signs (unlike Delirium Tremens).
- Delirium Tremens (DT) (48–96 hours): Life-threatening emergency characterized by delirium (clouded sensorium/disorientation), severe autonomic instability (fever, severe tachycardia, hypertension), and diaphoresis. Mortality rate is ~5%.
Management involves symptom-triggered benzodiazepines (Diazepam, Chlordiazepoxide) using the CIWA-Ar protocol. In patients with advanced liver dysfunction (cirrhosis), hepatitis, or elderly patients, use short-acting benzodiazepines cleared strictly by glucuronidation without active metabolites: Lorazepam, Oxazepam, Temazepam (LOT).
Diagnostic & Management Algorithm for Acute Psychotropic Syndromes
Diagnostic & Treatment Algorithm for Psychotropic Emergencies:
1. Suspected Hyperthermic / Autonomic Instability Syndrome:
- History of Serotonergic drugs (SSRI, SNRI, MAOI, Tramadol, MDMA) + Hyperreflexia, Inducible Clonus, Tremor, Mydriasis, Bowel hypermotility -> Serotonin Syndrome.
-> Treatment: Discontinue serotonergic agents, supportive care, IV fluids, Benzodiazepines; administer Cyproheptadine if severe.
- History of Antipsychotic exposure + "Lead-pipe" muscle rigidity, Hyporeflexia, Extreme Hyperthermia, Autonomic Instability, Elevated CK -> Neuroleptic Malignant Syndrome (NMS).
-> Treatment: Discontinue antipsychotics, aggressive cooling, IV fluids, ICU monitoring; administer Dantrolene or Bromocriptine.
- History of Anticholinergic exposure (TCAs, Diphenhydramine) + Mydriasis, Anhidrosis ("Dry as a bone"), Flushing ("Red as a beet"), Delirium ("Mad as a hatter"), Urinary retention -> Anticholinergic Toxicity.
-> Treatment: Supportive care, Benzodiazepines for agitation, Physostigmine (central and peripheral cholinesterase inhibitor).
2. Suspected Substance Overdose / Withdrawal:
- Miosis, Respiratory Depression, Hypothermia, Bradycardia -> Opioid Overdose -> Immediate IV/Intranasal Naloxone.
- Tremor, Tachycardia, Hypertension, Agitation, Hallucinosis, Seizures 48-96h post-ingestion -> Delirium Tremens -> High-dose IV Benzodiazepines (Diazepam, Lorazepam).
Maintenance Pharmacotherapy for Substance Use Disorders
Long-term management of substance dependence combines evidence-based pharmacotherapy with psychosocial interventions.
| Medication | Mechanism of Action | Primary Indication | Key Contraindications / Monitoring |
|---|---|---|---|
| Naltrexone | Mu-opioid receptor antagonist | First-line Alcohol Use Disorder & Opioid Use Disorder maintenance | Contraindicated in acute hepatitis, liver failure, or active opioid use |
| Acamprosate | Glutamate NMDA receptor modulator | Alcohol Use Disorder maintenance (reduces craving) | Safe in liver disease; dose-adjust or avoid in severe renal impairment (CrCl <30) |
| Disulfiram | Aldehyde dehydrogenase inhibitor | Alcohol Use Disorder (aversion therapy) | Causes severe acetaldehyde accumulation if alcohol consumed; requires high motivation |
| Buprenorphine | Partial mu-opioid agonist / kappa antagonist | Opioid Use Disorder maintenance | Can precipitate withdrawal if administered while full mu-agonists are active |
| Methadone | Long-acting full mu-opioid agonist | Opioid Use Disorder maintenance | Risk of QTc prolongation, respiratory depression; strictly regulated clinic dispensing |
| Varenicline | Alpha-4 beta-2 nicotinic acetylcholine partial agonist | Tobacco Use Disorder cessation | Monitor for neuropsychiatric symptoms and vivid dreams; superior efficacy to NRT |
Substance Intoxication & Withdrawal Differential
- Opioids:
- Intoxication: Miosis (pinpoint pupils), CNS depression, respiratory depression, decreased bowel sounds, bradycardia, hypothermia. Reversal: Naloxone.
- Withdrawal: Mydriasis (dilated pupils), lacrimation, rhinorrhea, piloerection ("cold turkey"), nausea, abdominal cramping, diarrhea, yawning, muscle aches. Management: Buprenorphine, Methadone, or Clonidine (for autonomic symptoms).
- Stimulants (Cocaine, Amphetamines):
- Intoxication: Mydriasis, hypertension, tachycardia, psychomotor agitation, paranoia, chest pain, myocardial infarction, aortic dissection. Management: Benzodiazepines (avoid unopposed alpha-stimulation with pure beta-blockers in acute cocaine chest pain).
- Withdrawal: Severe dysphoria, "crash", hypersomnia, hyperphagia, vivid dreams, psychomotor retardation.
- Sedatives/Hypnotics (Benzodiazepines, Barbiturates):
- Intoxication: Slurred speech, ataxia, somnolence, respiratory depression (marked when combined with alcohol). Reversal: Flumazenil (competitive GABA antagonist; use with caution due to risk of precipitating withdrawal seizures in chronic users).
- Withdrawal: Autonomic hyperactivity, tremor, insomnia, anxiety, generalized seizures (life-threatening).
Psychotropic Toxicity & Adverse Syndromes
Serotonin Syndrome vs. Neuroleptic Malignant Syndrome vs. Anticholinergic Toxicity
Recognizing hyperthermic psychiatric emergencies is high-yield for Step 2 CK.
- Serotonin Syndrome: Caused by combination or overdose of serotonergic agents (e.g., SSRIs + MAOIs, Linezolid, Tramadol, MDMA). Onset is rapid (<24 hours). Key physical signs: Hyperreflexia, neuromuscular clonus (spontaneous, inducible, or ocular), tremor, mydriasis, hyperactive bowel sounds, diarrhea, diaphoresis, and fever. Treatment: Discontinue serotonergic drugs, supportive care, IV fluids, benzodiazepines; administer Cyproheptadine (5-HT antagonist) in severe cases.
- Neuroleptic Malignant Syndrome (NMS): Caused by D2 antagonists. Onset is gradual (days to weeks). Key physical signs: "Lead-pipe" muscle rigidity, hyporeflexia, extreme hyperthermia (>40°C/104°F), autonomic instability, marked elevation of creatine kinase (CK), leukocytosis, and rhabdomyolysis. Treatment: Discontinue antipsychotic, ICU monitoring, aggressive cooling, IV hydration, and Dantrolene (skeletal muscle relaxant) or Bromocriptine / Amantadine (dopamine agonists).
- Anticholinergic Toxicity: Caused by TCAs, antihistamines (diphenhydramine), atropine. Features: "Flushed as a beet, dry as a bone, blind as a bat, mad as a hatter, hot as a hare, full as a flask" (mydriasis, anhidrosis, flushing, delirium, hyperthermia, urinary retention, absent bowel sounds). Treatment: Physostigmine.
A 52-year-old man with a long history of severe alcohol use disorder is admitted to the hospital for elective orthopedic surgery. On postoperative day 3 (approximately 72 hours after his last drink), he becomes acutely disoriented, agitated, and diaphoresis is noted. His temperature is 38.9°C (102.0°F), blood pressure is 168/102 mm Hg, and heart rate is 124/min. Physical examination reveals drenching sweat, coarse tremors, and visual hallucinations of insects crawling on the wall. What is the most likely diagnosis?
A 45-year-old woman with a history of alcohol use disorder comes to the outpatient clinic seeking pharmacotherapy to help maintain abstinence. Laboratory testing demonstrates normal serum bilirubin and transaminases, but her serum creatinine is 0.9 mg/dL. She does not use any opioids. Which medication is a first-line option for preventing relapse by blocking mu-opioid receptors?
A 24-year-old woman is brought to the emergency department after experiencing a generalized seizure at a music festival. Her roommate reports she took fluoxetine daily for depression and ingested an unknown recreational pill 4 hours ago. On examination, her temperature is 39.2°C (102.6°F), blood pressure is 154/92 mm Hg, and heart rate is 118/min. She is agitated, diaphoretic, and exhibits bilateral ocular clonus, inducible ankle clonus, hyperreflexia, and hyperactive bowel sounds. Which diagnosis is most consistent with these findings?