Differentiating and Treating Cocaine versus Mercury Toxicity
Cocaine and mercury toxicity present with distinctly different clinical syndromes that allow rapid differentiation: cocaine causes an acute sympathomimetic toxidrome with cardiovascular collapse, while mercury causes delayed renal failure with chemical burns at exposure sites.
Clinical Differentiation
Cocaine Toxicity Presentation
- Acute sympathomimetic toxidrome: tachycardia, hypertension, hyperthermia, seizures, diaphoresis, and increased psychomotor activity within minutes to hours of exposure 1
- Cardiovascular manifestations: chest pain, dysrhythmias (wide-complex tachycardia, QRS prolongation), coronary vasospasm, and acute coronary syndrome 1
- Neurological symptoms: agitation, psychosis, altered mental status, and seizures from CNS stimulation 1
- ECG changes: QRS prolongation from sodium channel blockade, QT prolongation from potassium channel blockade, and potentially Brugada pattern 1
- Timing: symptoms develop rapidly (minutes to hours) after exposure 2
Mercury Toxicity Presentation
- Local chemical burns: severe nasal cavity burns if administered intranasally, mimicking the route of cocaine use 3
- Delayed renal dysfunction: develops from day 2 onward with transient polyuria and nitrogen retention 3
- Hypertension with elevated catecholamines: can simulate pheochromocytoma, often with rash and painful extremities (acrodynia) 4
- Timing: systemic symptoms develop over days, not acutely 3, 4
- Laboratory findings: markedly elevated urine mercury levels (>1000 μg/L in severe cases) 3
Treatment of Cocaine Toxicity
Immediate Life-Threatening Complications
For hyperthermia:
- Rapid external cooling using evaporative or immersive methods (NOT cooling blankets or cold packs) 5
For wide-complex tachycardia or cardiac arrest:
- Administer sodium bicarbonate to reverse sodium channel blockade 5
- Administer lidocaine for wide-complex tachycardia through competitive sodium channel binding 5
For coronary vasospasm or hypertensive emergencies:
- Administer vasodilators: nitrates, phentolamine, or calcium channel blockers (verapamil) to improve coronary blood flow 5
- Benzodiazepines (lorazepam, diazepam) for hypertension, tachycardia, and agitation 5, 6
Critical Pitfall
- Never use β-blockers within 72 hours of cocaine use as they potentiate coronary vasospasm through unopposed α-adrenergic stimulation 6
Supportive Management
- Benzodiazepines are the foundation for controlling agitation, seizures, and sympathomimetic symptoms 6
- Morphine and sublingual nitroglycerin for chest pain 5
- Monitor for complications: myocardial infarction, aortic dissection, rhabdomyolysis, mesenteric ischemia 2
Treatment of Mercury Toxicity
Chelation Therapy
- DMPS (dimercaptopropanesulfonate) as primary chelating agent 3
- N-acetylcysteine as adjunctive therapy 3
- D-penicillamine as additional chelation option 3
Renal Support
- Hemodialysis for renal dysfunction, performed simultaneously with chelation therapy to accelerate mercury elimination 3
- DMPS appears safe during hemodialysis even with renal impairment 3
- Monitor for polyuria and nitrogen retention starting day 2 3
Local Treatment
- Address chemical burns at exposure sites (nasal cavity if intranasal exposure) 3
Monitoring
- Serial urine mercury levels to guide treatment duration (target: return to physiological levels <20 μg/L) 3
- Renal function monitoring throughout treatment course 3
Key Distinguishing Features for Rapid Diagnosis
| Feature | Cocaine | Mercury |
|---|---|---|
| Onset | Minutes to hours | Days |
| Cardiovascular | Acute tachycardia, hypertension, chest pain | Delayed hypertension with elevated catecholamines |
| Renal | Acute injury from rhabdomyolysis | Delayed dysfunction with polyuria (day 2+) |
| Local signs | None specific | Chemical burns at exposure site |
| Mental status | Agitation, psychosis, seizures | Variable, less acute |
| ECG | Wide QRS, QT prolongation, dysrhythmias | Normal or hypertensive changes |
Clinical Caveat
- One case report describes accidental intranasal mercury chloride exposure mistaken for cocaine, presenting with both local nasal burns AND delayed renal failure—the combination of immediate local injury with delayed systemic toxicity distinguishes mercury from cocaine's purely acute sympathomimetic presentation 3