Amphetamines are potent central nervous system (CNS) stimulants used medically for ADHD and narcolepsy but widely misused for their euphoric and performance-enhancing effects. Toxicity results from excessive sympathetic stimulation and CNS excitation. Severe overdose can lead to life-threatening complications, making early recognition and management essential.
Mechanism of Action
- Increases release of dopamine, norepinephrine, and serotonin
- Blocks reuptake of monoamines at synaptic clefts
- Strong sympathomimetic activation → tachycardia, hypertension, hyperthermia
Clinical Features
Central Nervous System
- Euphoria and heightened alertness
- Agitation, restlessness
- Tremors
- Seizures in severe toxicity
- Psychosis: hallucinations, delusions
Cardiovascular
- Tachycardia and hypertension
- Arrhythmias
- Chest pain due to coronary vasospasm
- Risk of myocardial infarction or stroke
Other Symptoms
- Hyperthermia
- Dry mouth
- Mydriasis
- Rhabdomyolysis
- Urinary retention
Complications
- Hyperthermic injury → DIC, renal failure
- Severe hypertension → intracranial hemorrhage
- Cardiac arrhythmias
- Rhabdomyolysis
- Seizures leading to hypoxia
Diagnosis
- Clinical toxidrome recognition (sympathomimetic)
- Urine toxicology screen
- Electrolytes, renal function
- Creatine kinase (for rhabdomyolysis)
- ECG for arrhythmias
- Temperature monitoring for hyperthermia
Management
1. Supportive Care (Mainstay of Treatment)
- Ensure airway, breathing, and circulation
- IV fluids for hydration and temperature control
2. Sedation
- Benzodiazepines are first-line for agitation and seizures
- Avoid antipsychotics unless absolutely necessary (risk of lowering seizure threshold)
3. Hyperthermia Management
- External cooling measures (cooling blankets, ice packs)
- Avoid antipyretics—they do not help in drug-induced hyperthermia
4. Cardiovascular Management
- Short-acting antihypertensives (e.g., nitroprusside) for severe hypertension
- Avoid beta-blockers alone (risk of unopposed alpha stimulation)
5. Rhabdomyolysis Treatment
- Aggressive IV fluids
- Monitor urine output
- Alkalinization of urine if needed
6. Psychiatric Care
- Treat amphetamine-induced psychosis with supportive care and benzodiazepines
- Consider referral for addiction management programs
Prevention and Harm Reduction
- Avoid mixing amphetamines with alcohol or other stimulants
- Educate on overdose symptoms
- Promote safe prescription use
Detailed Notes:
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PATH: PHARMD/ PHARMD NOTES/ PHARMD FOURTH YEAR NOTES/ CLINICAL TOXICOLOGY/ CNS STIMULANTS: AMPHETAMINE.