What is the treatment for methamphetamine intoxication?

Treatment for Methamphetamine Intoxication

Benzodiazepines are the first-line treatment for methamphetamine intoxication, managing agitation, hypertension, tachycardia, and psychosis, while beta-blockers must be strictly avoided due to risk of worsening coronary vasospasm. 1, 2, 3

Immediate Pharmacological Management

Primary Treatment: Benzodiazepines

• Administer benzodiazepines as the cornerstone of therapy for all sympathomimetic manifestations including agitation, hypertension, tachycardia, and psychosis 2, 3, 4
• Benzodiazepines work by addressing both central and peripheral manifestations of acute intoxication through their anxiolytic and muscle relaxant properties 1
• Oral sedation successfully manages acute behavioral disturbance in approximately 61% of cases, with parenteral administration reserved for refractory agitation 5

Adjunctive Cardiovascular Management

• Combine benzodiazepines with nitroglycerin for enhanced control of hypertension and tachycardia when benzodiazepines alone are insufficient 1, 2, 3
• For chest pain with suspected coronary vasospasm, administer sublingual nitroglycerin or intravenous calcium channel blockers (e.g., diltiazem 20 mg IV) as first-line therapy 2, 3
• Calcium channel blockers are particularly effective because methamphetamine causes direct coronary vasoconstriction through alpha-adrenergic stimulation 1

Critical Contraindications

Beta-Blocker Avoidance

• Never administer beta-blockers in acute methamphetamine intoxication showing signs of euphoria, tachycardia, or hypertension 1, 2, 3
• Beta-blockers cause unopposed alpha-adrenergic stimulation, paradoxically worsening coronary vasospasm and potentially precipitating myocardial infarction 1, 2
• This contraindication applies even to combined alpha-beta blockers, which should be avoided entirely in acute intoxication 2, 3
• Patients with remote methamphetamine use history but no acute intoxication signs can receive standard therapies including beta-blockers if otherwise indicated 2

Cardiovascular Complications Management

Acute Coronary Syndrome Assessment

• Obtain immediate 12-lead ECG upon presentation to evaluate for ischemia, arrhythmias, or ST-elevation 2
• Measure cardiac biomarkers (troponin) to assess for myocardial injury, as methamphetamine causes true myocardial infarction through coronary vasospasm, thrombosis, or plaque rupture 1, 2
• ST-elevation meeting STEMI criteria (≥1 mm in two contiguous limb leads or ≥2 mm in precordial leads) requires urgent evaluation regardless of methamphetamine attribution 2

Treatment Algorithm for Chest Pain

• First-line: Sublingual nitroglycerin or IV calcium channel blockers for suspected vasospasm 2, 3
• If ST elevation persists despite nitroglycerin and calcium channel blockers, or if cardiac biomarkers are positive, proceed to immediate coronary angiography 2
• Manage as non-ST-elevation acute coronary syndrome when appropriate, but maintain beta-blocker avoidance 2

Monitoring and Observation

Observation Protocols

• Patients with ECG changes and normal initial cardiac biomarkers require monitored observation for 9-24 hours, as most methamphetamine-related cardiac complications occur within this timeframe 2
• A shorter 9-12 hour observation with serial troponin measurements at 3,6, and 9 hours may be appropriate in select lower-risk cases 2
• The majority (84%) of methamphetamine presentations are managed solely within the emergency department with median length of stay of 14 hours 5

Life-Threatening Complications

Severe Hyperthermia Management

• For temperature >40°C with continued agitation despite maximal benzodiazepine sedation, proceed immediately to intubation 2, 3
• Use nondepolarizing paralytic agents (avoid succinylcholine due to hyperkalemia risk from rhabdomyolysis) and initiate aggressive cooling measures including chilled saline bolus and external cooling 2
• Continued agitation at extreme temperatures indicates inability to control metabolic heat production and imminent risk of rhabdomyolysis, renal failure, seizures, and death 2
• Every minute of delay at high temperatures causes irreversible organ damage 2

Rhabdomyolysis and Renal Protection

• Monitor for rhabdomyolysis, which occurs in approximately 30% of presentations with significant complications 5
• Maintain aggressive urine output with IV fluids, and consider furosemide and mannitol to prevent myoglobin-induced renal failure 2
• Treat hyperkalemia with dextrose, insulin, and calcium chloride as needed 2

Common Pitfalls to Avoid

• Do not delay definitive treatment while attempting urinary acidification strategies, as the ascorbic acid doses required (≥12 g/day) are impractical, show no significant effect at standard doses, and are potentially nephrotoxic 3
• Do not underestimate cardiovascular risk: methamphetamine causes real acute coronary syndromes even in patients with normal coronary arteries through vasospasm and enhanced platelet aggregation 1, 2
• Do not rely on clinical presentation alone, as up to 30% of STEMI patients present atypically, and methamphetamine users frequently mask true cardiac events 2
• Acute kidney injury occurs in 13% of presentations, requiring vigilant monitoring 5

Expected Outcomes

• With appropriate symptom-directed supportive care centered on benzodiazepines, most patients make full recovery 4
• Mortality in severe sympathomimetic toxicity with hyperthermia approaches 11%, with significant morbidity from rhabdomyolysis, renal failure, seizures, and disseminated intravascular coagulation 2
• Serious complications beyond rhabdomyolysis and acute kidney injury are rare, including seizures (0.5%), intracranial hemorrhage (0.8%), and myocardial infarction (0.3%) 5