Amphetamines

Question 1

Discuss the lethal complications of sympathomimetics.

Answer 1

Severe hyperthermia, ACS, cardiac dysrhythmias, aortic dissection and ICH. Long-term neuropsychiatric complications.

Question 2

What proportion of emergency presentations with amphetamines are associated with seizures?

Answer 2

4%

Question 3

What symptoms warrant aggressive management and investigation in amphetamine abuse?

Answer 3

Chest pain, focal neurological signs, altered level of conciousness, hyperthermia, headaches. Suggest potentially life-threatening complications

Question 4

How do amphetamines work?

Answer 4

Enhance catecholamine release and block reuptake + inhibition of monoamine oxidase. The result is CNS/PNS NA, dopaminergic, serotonergic stimulation occurs.

Question 5

What is a syndrome that MDMA can induce?

Answer 5

SIADH - profound hyponatraemia, coma and convulsions

Question 6

What receptors do amphetamines affect? What is the long-term consequence?

Answer 6

Permanent destruction of dopaminergic neuro-pathways; neurotransmitter and receptor adaptation also occurs

Question 7

Describe the toxicokinetics for amphetamines.

Answer 7

Well-absorbed, lipid-soluble bases and have VoD of 3.5L/kg. Undergo hepatic metabolism with urinary excretion. Half-life of 8-30 hours.

Question 8

What are the clinical features of amphetamine intoxication?

Answer 8

CNS: euphoria, paranoia, hyperthermia, rigidity, myoclonic movements, seizures, hallucinations. CV: tachy, hypertension, dysrhythmias, ACS, cardiomyopathy, APO. Peripheral: mydriasis, sweating, tremor. Others: rhabdo, dehydration, AKI, hyponatraemia, vessel dissection, SAH, ICH, ischaemic colitis.

Question 9

Discuss ACS in amphetamine overdose.

Answer 9

Avoid beta-blockers; ACS is usually due to dissection or vasospasm not thrombosis. Thrombolysis is not appropriate.

Question 10

How do you manage amphetamine induced tachycardia and hypertension?

Answer 10

Benzodiazepines, phentolamine 1 mg IV Q5min, titrated vasodilator infusion (SNP, GTN) but avoid beta-blockers

Question 11

Discuss hyponatraemia management with amphetamine overdose.

Answer 11

Immediate correction with sodium chloride 3% is indicated if Na <120 + seziures/ALOC. Give hypertonic 3% 4 ml/kg over 30 minutes and repeat sodium. Continue until hyponatraemia/SIADH resolves spontaneously.

Question 12

Why are beta blockers contraindicated in amphetamine toxicity?

Answer 12

Leads to unopposed alpha-stimulation and vasoconstriction