Drugs of Abuse, Sympathomimetic Toxicity & Opioid Crises
Comprehensive emergency toxicology protocol for acute sympathomimetic toxidromes (cocaine, methamphetamines, MDMA, synthetic cathinones), excited delirium syndrome, malignant hyperthermia, and opioid overdose and withdrawal. Covers aggressive benzodiazepine sedation, ice-water immersion cooling, coronary vasospasm management, the unopposed alpha-stimulation controversy, and precision naloxone titration.
Resuscitation Quick Actions • First 2 Minutes
Malignant Hyperthermia Target
Temp > 40°C is an emergency: immediately submerge in ice-water bath or apply active evaporative cooling targeting core temp < 38.5°C
High-Dose Sedation
Diazepam 5-10 mg IV or Lorazepam 2-4 mg IV every 5-10 minutes until calm; under-dosing sedation leads to rhabdomyolysis and arrest
The Cocaine Beta-Blocker Rule
Avoid pure beta-blockers in acute cocaine/meth toxicity; treat tachycardia/HTN with Benzodiazepines + Nitroglycerin/Phentolamine
Precision Naloxone Titration
Administer Naloxone 0.04-0.1 mg IV initial dose in breathing patients to reverse hypoventilation without precipitating acute violent withdrawal
Synthetic Cannabinoids (K2)
Potent full cannabinoid agonists: cause profound seizures, catatonia, ischemic stroke, and acute kidney injury
Bottom-Line Clinical Pearl
In severe sympathomimetic toxicity with psychomotor agitation and hyperthermia (temperature > 39.5-40°C), immediate ice-water immersion and high-dose intravenous Benzodiazepines (e.g., Lorazepam 2-4 mg or Diazepam 5-10 mg every 5-10 minutes) are life-saving. In cocaine-induced chest pain or hypertension, avoid pure beta-blockers (propranolol/metoprolol) due to unopposed alpha-adrenergic coronary vasoconstriction; treat with Benzodiazepines, Nitroglycerin, and Phentolamine.
Sympathomimetic agents (Cocaine, Methamphetamine, MDMA/Ecstasy, Synthetic Cathinones ['Bath Salts']) produce profound central and peripheral sympathetic nervous system activation via presynaptic release and reuptake inhibition of norepinephrine, dopamine, and serotonin:
| Clinical Feature | Sympathomimetic Overdose | Anticholinergic Overdose (Distinction) |
|---|---|---|
| Skin & Secretions | PROLONGED PROFUSE DIAPHORESIS: Skin is hot, flushed, and soaked with perspiration. Mucous membranes may be dry or moist. | COMPLETELY DRY/ANHIDROTIC: Absence of sweating; skin is flushed, hot, and dry ('dry as a bone'). Axillae and groin are completely dry. |
| Pupils & Eye Signs | Mydriasis (dilated pupils) with preserved pupillary light reflex. | Extreme mydriasis; non-reactive or sluggish to light; cycloplegia (paralysis of accommodation, blurred near vision). |
| Bowel Sounds & Bladder | Normal or hyperactive bowel sounds; urinary retention is uncommon. | Hypoactive or absent bowel sounds; severe acute urinary retention with distended palpable bladder. |
| Life-Threatening Crises | Malignant hyperthermia (temp > 40-41°C), rhabdomyolysis, acute renal failure, aortic dissection, myocardial infarction, and intracranial hemorrhage. | Delirium, seizures, wide-complex dysrhythmias (if TCA/diphenhydramine), central anticholinergic psychosis ('mad as a hatter'). |
| Therapeutic Domain | Emergency Action & Dosing Protocol | Clinical Rationale & High-Yield Pitfalls |
|---|---|---|
| First-Line Pharmacotherapy | High-Dose Intravenous Benzodiazepines: - Diazepam 5 to 10 mg IV every 5–10 minutes OR - Lorazepam 2 to 4 mg IV every 5–10 minutes. Titrate to a calm, lightly sedated state (RASS -1 to -2). Patients in excited delirium often require massive cumulative doses (e.g., 50–100 mg of diazepam). | Benzodiazepines enhance central GABA-A neurotransmission, directly dampening sympathomimetic outflow, reducing heart rate and blood pressure, terminating muscle contractions, and halting metabolic heat production. Avoid haloperidol or second-generation antipsychotics as monotherapy (worsens hyperthermia and lowers seizure threshold). |
| Hyperthermia Resuscitation | If core temperature > 39.5°C (103°F): 1. Initiate Rapid Ice-Water Immersion or continuous evaporative misting with high-velocity fans. 2. Infuse cold isotonic crystalloids (4°C normal saline). 3. Endotracheal intubation with neuromuscular paralysis (Vecuronium or Rocuronium; AVOID Succinylcholine due to hyperkalemic cardiac arrest in rhabdomyolysis!). | Malignant hyperthermia in sympathomimetic toxicity is driven by excessive psychomotor agitation and muscle hyperactivity, NOT hypothalamic set-point elevation. Antipyretics (Acetaminophen, Ibuprofen) are completely ineffective. Target core temperature < 38.5°C within 30 minutes to prevent fatal DIC, hepatic necrosis, and cerebral edema. |
| The 'Unopposed Alpha-Stimulation' Controversy | In acute cocaine-induced chest pain or severe hypertension, AVOID PURE BETA-BLOCKERS (e.g., Metoprolol, Propranolol, Atenolol). First-line: Benzodiazepines + IV Nitroglycerin. Second-line: Phentolamine (alpha-adrenergic antagonist, 1–5 mg IV) or Diltiazem (calcium channel blocker). | Cocaine stimulates both alpha-1 (vasoconstriction) and beta-2 (vasodilation) receptors in coronary arteries. Administering a pure beta-blocker eliminates beta-2-mediated vasodilation while leaving alpha-1 adrenergic stimulation unopposed, precipitating coronary spasm, myocardial infarction, and severe paradoxical hypertension. Labetalol (combined alpha/beta blocker with 1:7 ratio) is considered acceptable by some guidelines but pure vasodilators are safer. |
The classic opioid toxidrome comprises miosis (pinpoint pupils), central respiratory depression (respiratory rate < 8-10 breaths/min), and depressed mental status/coma. Death results from fatal hypoxic hypercapnic respiratory arrest:
- The Goal of Naloxone Administration: The therapeutic endpoint of Naloxone (Narcan) is NOT full neurological arousal, but the restoration of adequate spontaneous alveolar ventilation (respiratory rate >= 10-12 breaths/min with normal tidal volume). Awakening the patient completely precipitates acute violent withdrawal, agitation, vomiting with pulmonary aspiration, and refusal of medical care.
- Precision Dosing Strategy: In a spontaneously breathing but hypoventilating patient with a pulse: administer Naloxone 0.04 to 0.1 mg IV (or 0.4 mg intranasal/IM). Double the dose every 2 minutes if no respiratory improvement is observed (0.04 mg -> 0.1 mg -> 0.2 mg -> 0.4 mg -> 2.0 mg). In cardiac arrest or profound apnea: administer Naloxone 2.0 mg IV push immediately.
- Synthetic Opioid Nuances: High-potency synthetic opioids (Fentanyl, Carfentanil) and long-acting methadone may require higher cumulative doses of naloxone and continuous intravenous infusion (titrated at two-thirds of the effective wake-up bolus dose per hour) because naloxone's half-life is only 30 to 60 minutes.
Sympathomimetic Malignant Hyperthermia: Minutes to Multiorgan Collapse
In severe cocaine, methamphetamine, or synthetic cathinone ('bath salts') toxicity, psychomotor agitation drives cellular metabolic heat production faster than the body can dissipate it. When core body temperature exceeds 40.5°C (105°F), cellular thermal injury triggers acute rhabdomyolysis, diffuse intravascular coagulation (DIC), hyperkalemic cardiac arrest, and irreversible anoxic-ischemic encephalopathy within 30 to 60 minutes. Antipyretics are 100% useless. Immediately submerge the patient in an ice-water bath or employ continuous evaporative water-mist and fan cooling, and administer aggressive IV Benzodiazepines (Diazepam 10 mg IV q5min). If the patient is thrashing or combative, perform rapid sequence intubation with non-depolarizing paralytics (Vecuronium or Rocuronium; NEVER Succinylcholine) to eliminate skeletal muscle thermogenesis instantly.
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