Sympathomimetic toxicity is a clinical toxidrome resulting from excessive adrenergic nervous system activation caused by substances such as amphetamines, cocaine, cathinones (bath salts), synthetic cannabinoids, and MDMA. The hallmark features are tachycardia, hypertension, hyperthermia, agitation, and mydriasis, and the cornerstone of treatment is benzodiazepines and aggressive supportive care — there is no direct antidote. [1-2]
1. History
- Substance used: What was taken? (amphetamine, methamphetamine, cocaine, MDMA, bath salts/cathinones, synthetic cannabinoids, prescription stimulants, OTC decongestants)
- Route: Oral, intranasal, IV, smoked, rectal — IV and smoked routes have fastest onset
- Timing: When was the substance used? Onset typically minutes (smoked/IV) to 30–60 min (oral)
- Amount/dose: How much? Intentional overdose vs recreational use vs accidental pediatric ingestion
- Co-ingestants: Polydrug use is extremely common — ask about opioids, alcohol, benzodiazepines, GHB, other stimulants [3]
- Progression: Worsening agitation, chest pain, palpitations, seizures, confusion
- Associated symptoms: Chest pain, headache, dyspnea, visual changes, abdominal pain, muscle pain/weakness
- Important negatives: No trauma, no fever source, no psychiatric history of mania
2. Alarm Features
- Core temperature >40°C (104°F) — rapidly life-threatening and associated with mortality [1]
- Seizures or status epilepticus [1][3]
- Chest pain with ECG changes — concern for vasospasm-induced MI even in young patients with normal coronaries [1][4]
- Severe hypertension (SBP >180) with end-organ damage (headache, visual changes, AKI)
- Cardiac arrest — may present as VF, VT, or PEA [1-2]
- Severe metabolic acidosis (pH <7.0) — marker of critical illness [3]
- Rhabdomyolysis with dark urine, muscle rigidity
- Altered mental status / unresponsive agitation (excited delirium)
- Prolonged physical restraint without sedation — associated with death [1-2]
3. Medications
Causative agents:
- Illicit: Cocaine, methamphetamine, MDMA, cathinones (mephedrone, N-ethylpentylone), synthetic cannabinoids [1-2]
- Prescription: Amphetamine salts (Adderall), methylphenidate, lisdexamfetamine, pseudoephedrine, phenylephrine
- OTC/supplements: Ephedra, caffeine in massive doses
First-line treatment:
- Benzodiazepines (first-line GABAergic agent): Diazepam 5–10 mg IV q5 min or midazolam 5 mg IV/IM q5 min — large doses may be required [2][5]
- Phenobarbital, propofol as second-line GABAergic agents for refractory agitation [5-6]
Adjunctive agents (if hyperadrenergic state persists after adequate sedation):
- Alpha-2 agonists: Dexmedetomidine (severe symptoms), clonidine (mild-moderate) [5-6]
- Mixed alpha-beta blockers: Labetalol or carvedilol (if beta-blocker needed) [5-6]
- CCBs, alpha-1 antagonists (phentolamine), nitrates for refractory hypertension/vasospasm [2][5]
- Nitroglycerin if signs of cardiac ischemia [5]
Contraindicated / use with caution:
- Pure beta-blockers (e.g., propranolol, metoprolol) — risk of unopposed alpha stimulation, worsening hypertension and vasospasm, especially with cocaine [5-6]
- Long-acting antihypertensives — risk of abrupt hemodynamic collapse as stimulant wears off [5]
- Dantrolene — conflicting data for MDMA-induced hyperthermia; not standard of care [1]
- Avoid succinylcholine in suspected rhabdomyolysis (hyperkalemia risk)
4. Diet
- NPO if severely agitated or altered mental status
- Aggressive IV fluid resuscitation — critical for rhabdomyolysis management; target urine output >2 mL/kg/h [6]
- Correct electrolyte abnormalities (hyperkalemia, hyponatremia)
- Avoid urinary alkalinization in amphetamine-related rhabdomyolysis — it inhibits amphetamine elimination [6]
- Long-term: Adequate hydration, balanced nutrition during recovery from stimulant use disorder
5. Review of Systems
- Cardiovascular: Chest pain, palpitations, dyspnea
- Neurologic: Headache, seizures, visual changes, focal weakness (stroke)
- Psychiatric: Paranoia, hallucinations (tactile — "formication" with cocaine), suicidal ideation
- GI: Nausea, vomiting, abdominal pain (mesenteric ischemia, body packing)
- Musculoskeletal: Muscle pain, weakness, dark urine (rhabdomyolysis)
- Genitourinary: Decreased urine output (AKI)
- Constitutional: Diaphoresis, feeling hot
6. Collateral History and Family History
- Collateral from EMS/bystanders: Witnessed substance use, paraphernalia at scene, duration of agitation, any seizure activity, restraint use
- Pharmacy records: Prescription stimulant use
- Family/social: History of substance use disorder, psychiatric illness, prior overdoses
- Body packing/stuffing: Travel history, law enforcement involvement
- Family history of cardiac arrhythmias, sudden cardiac death, or cardiomyopathy (lowers threshold for drug-induced events) [7]
7. Risk Factors
- Polysubstance use — dramatically increases mortality, especially stimulant + stimulant combinations [3]
- IV drug use — faster onset, higher peak levels, infection risk
- Pre-existing cardiovascular disease — coronary artery disease, cardiomyopathy, hypertension [7]
- Hot/humid environments — impaired heat dissipation
- Prolonged physical exertion (raves, festivals) combined with stimulant use
- Psychiatric comorbidities — may delay recognition of toxidrome
- Chronic stimulant use — structural cardiac changes, accelerated atherosclerosis [4]
- Young age — highest prevalence of stimulant use; however, MI can occur even in young patients with normal coronaries [1][4]
8. Differential Diagnosis
Key distinguishing feature of sympathomimetic toxidrome: Diaphoresis (wet skin) — differentiates from anticholinergic toxidrome (dry skin). [8]
9. Past Medical History
- Prior stimulant use or overdose episodes
- Cardiovascular disease: CAD, prior MI, cardiomyopathy, arrhythmias, hypertension
- Psychiatric history: Bipolar disorder, schizophrenia (may confound presentation)
- Seizure disorder
- Renal disease (lower threshold for AKI from rhabdomyolysis)
- Prior rhabdomyolysis
- Hepatic disease (altered drug metabolism)
- Pregnancy (risk of placental abruption, preeclampsia mimic)
10. Physical Exam
Vital signs (the toxidrome):
- Tachycardia (often >120 bpm)
- Hypertension (may be severe; SBP >200 possible)
- Hyperthermia — core temp >40°C is a critical threshold [1]
- Tachypnea
Focused exam:
- Eyes: Mydriasis (dilated, reactive pupils)
- Skin: Diaphoresis, warm, flushed — key differentiator from anticholinergic toxidrome [8]
- Neuro: Agitation, psychomotor hyperactivity, tremor, hyperreflexia, clonus (if serotonergic component), seizures
- Cardiovascular: Tachycardia, murmurs (endocarditis in IVDU), signs of heart failure
- Abdomen: Bowel sounds present (vs absent in anticholinergic); tenderness may suggest mesenteric ischemia or body packing
- Musculoskeletal: Muscle rigidity, tenderness (rhabdomyolysis)
- Skin survey: Track marks, skin popping scars, abscesses
11. Lab Studies
- BMP/CMP: Electrolytes (hyperkalemia from rhabdomyolysis), renal function (AKI), glucose, bicarbonate (metabolic acidosis) [6]
- VBG/ABG: Assess pH and lactate — severe acidosis (pH <7.0) is a poor prognostic sign [3]
- CK (creatine phosphokinase): Screen for rhabdomyolysis in any patient with agitation or hyperthermia [6]
- Troponin: Evaluate for myocardial injury/infarction [4]
- CBC: Leukocytosis (stress response), evaluate for infection
- Coagulation studies: DIC screening if severe
- Hepatic panel: Hepatic injury from hyperthermia/shock
- Urine drug screen: Helpful but limited — may not detect synthetic cathinones, novel psychoactive substances; cocaine metabolite (benzoylecgonine) detectable 2–4 days [4]
- Urinalysis: Myoglobinuria
- Serum ethanol, acetaminophen, salicylate: Rule out co-ingestants
12. Imaging
- Chest X-ray: If chest pain, dyspnea, or hypoxia — evaluate for pulmonary edema, pneumothorax, pneumomediastinum (from smoking/snorting)
- CT head (non-contrast): If seizures, focal neurologic deficits, severe headache, or altered mental status — rule out intracranial hemorrhage (stimulant-associated hypertensive hemorrhage)
- CT angiography of chest: If concern for aortic dissection (severe hypertension + tearing chest/back pain)
- Abdominal imaging (CT or KUB): If concern for body packing/stuffing
- Echocardiography: If hemodynamic instability, new murmur, or suspected takotsubo cardiomyopathy [1-2]
- Imaging is not routinely necessary in mild, uncomplicated sympathomimetic toxicity that resolves with sedation
13. Special Tests
- Point-of-care ultrasound (POCUS): Cardiac function (wall motion abnormalities, takotsubo pattern), IVC for volume status, FAST if trauma
- Urine myoglobin: If CK elevated
- Serum serotonin levels: Not clinically useful in acute setting
- Confirmatory toxicology (send-out): Gas chromatography–mass spectrometry for novel psychoactive substances if diagnosis unclear
- Poison Control / Medical Toxicology consultation: Recommended for severe or atypical presentations
14. ECG
Indications: All patients with sympathomimetic toxicity should receive an ECG.
Expected findings:
- Sinus tachycardia (most common) [4]
- ST-segment changes: Elevation or depression from vasospasm-induced ischemia [1][4]
- QRS prolongation: Particularly with cocaine (sodium channel blockade) — wide-complex tachycardia resembling Class Ia/Ic toxicity [1-2]
- QTc prolongation: Cocaine-related potassium channel blockade; risk of torsades de pointes [1-2]
- Ventricular tachycardia / ventricular fibrillation: Life-threatening arrhythmias [1-2]
- Takotsubo pattern: Deep T-wave inversions, ST elevation in anterior leads [1]
The following figure illustrates the progressive ECG changes seen with sodium channel blockade (relevant to cocaine toxicity specifically):
Pearl: QRS >100 ms in cocaine toxicity warrants sodium bicarbonate administration (1–2 mEq/kg IV bolus). [2]
15. Assessment
Severity stratification:
- Mild: Tachycardia, mild hypertension, anxiety, mydriasis, diaphoresis — responsive to verbal de-escalation and low-dose benzodiazepines
- Moderate: Significant agitation, hypertension (SBP >180), temperature 38–40°C, chest pain
- Severe/life-threatening: Core temp >40°C, seizures, cardiac arrest (VF/VT/PEA), severe metabolic acidosis, rhabdomyolysis with AKI, takotsubo cardiomyopathy, intracranial hemorrhage [1-3]
Complications to anticipate: Rhabdomyolysis → AKI, DIC, multiorgan failure, stress cardiomyopathy, coronary vasospasm → MI, intracranial hemorrhage, aortic dissection, mesenteric ischemia. [6]
16. Treatment Plan
Initial stabilization (ABCs):
- Airway management if GCS severely depressed or refractory seizures
- Continuous cardiac monitoring, pulse oximetry, core temperature monitoring
Agitation — the priority:
- Benzodiazepines first-line: Diazepam 5–10 mg IV or midazolam 5–10 mg IV/IM, repeat q5 min as needed — large cumulative doses may be required [2][5]
- Second-line: Phenobarbital, propofol (intubated patients), ketamine [2][5]
- Avoid prolonged physical restraint without chemical sedation — associated with death [1-2]
Hyperthermia (core temp >40°C):
- Aggressive external cooling — ice water immersion is fastest and preferred; evaporative cooling is an alternative [1]
- Cooling rate >0.15°C/min associated with improved survival [1]
- Antipyretics (acetaminophen) are ineffective — hyperthermia is from muscular/metabolic heat, not hypothalamic reset
Cardiovascular:
- Adequate sedation often resolves hypertension and tachycardia [2]
- Persistent hypertensive emergency: Short-acting agents — phentolamine, sodium nitroprusside, or dihydropyridine CCBs [5]
- Chest pain/ischemia: Nitroglycerin, CCBs, benzodiazepines; avoid pure beta-blockers [4-5]
- If labetalol or carvedilol is used, consult cardiology/toxicology [5]
- Takotsubo cardiomyopathy with cardiogenic shock: Consider VA-ECMO or IABP — often resolves spontaneously in days to weeks [1-2]
Seizures:
- Benzodiazepines first-line; phenobarbital or propofol for refractory seizures
- Avoid phenytoin (ineffective for toxin-induced seizures and may worsen cardiac conduction)
Rhabdomyolysis:
- Aggressive IV crystalloid resuscitation targeting urine output >2 mL/kg/h [6]
- Avoid urinary alkalinization with amphetamine-related rhabdomyolysis [6]
- Monitor CK, renal function, potassium serially
17. Disposition
Admit (ICU) if:
- Core temperature >40°C
- Cardiac arrest or life-threatening arrhythmias
- Seizures or status epilepticus
- Severe metabolic acidosis
- Hemodynamic instability requiring vasopressors or mechanical circulatory support
- Significant rhabdomyolysis (CK >5,000 or rising, AKI)
- Acute coronary syndrome or takotsubo cardiomyopathy
- Intracranial hemorrhage
Admit (telemetry/observation) if:
- Persistent tachycardia or hypertension despite sedation
- Troponin elevation
- Moderate rhabdomyolysis requiring IV fluids
- Ongoing need for repeated benzodiazepine dosing
Discharge criteria:
- Vital signs normalized and stable for ≥4–6 hours off sedation
- Asymptomatic, ambulatory, tolerating PO
- Normal mental status
- No evidence of end-organ damage
- Safe disposition (not suicidal, has follow-up)
Consult triggers:
- Medical toxicology / Poison Control — severe or atypical presentations
- Cardiology — ACS, arrhythmias, cardiomyopathy, need for mechanical support
- Nephrology — AKI requiring dialysis
- Psychiatry / Addiction medicine — substance use disorder, suicidality [5]
18. Follow Up / Return Precautions
- Follow-up timing: PCP or addiction medicine within 1–2 weeks; cardiology if cardiac involvement
- Return immediately for: Chest pain, palpitations, seizures, dark urine, decreased urine output, fever, confusion, severe headache, weakness
- Counseling points:
- No direct antidote exists — supportive care is the treatment [2]
- Stimulant use can cause MI and stroke even in young, healthy individuals [1][4]
- Polydrug use dramatically increases risk of death [3]
- Offer referral to addiction medicine / substance use disorder treatment [5]
- Harm reduction: Avoid using alone, avoid mixing substances, stay hydrated, avoid hot environments
- Expected course: Mild toxicity typically resolves within 4–8 hours (cocaine shorter, methamphetamine longer — up to 24 h). Takotsubo cardiomyopathy, if present, often resolves in days to weeks [1-2]
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