Clinical Toxicology

Question 1

When is enhanced elimination (activated charcoal every 4hrs) indicated?

Answer 1

Overdose of: carbamazepine, dapsone, phenobarbital, quinine, theophylline

Question 2

For what drugs is gastric lavage (requiring endotracheal intubation) indicated?

Answer 2

Iron and lithium overdose

Question 3

When is activated charcoal administration indicated?

Answer 3

Overdose of (within 1hr of ingestion)
aspirin
paracetamol
barbiturates
TCA’s
digoxin
amphetamines
morphine
cocaine
phenothiazines

Question 4

What levels of aspirin consumption can cause toxicity?

Answer 4

o <125mg/kg – unlikely to have severe toxicity

o >500mg/kg – possibly fatal

Question 5

Describe the presentation of aspirin overdose

Answer 5

• initial respiratory alkalosis (hyperventilation) followed by severe metabolic acidosis
o Nausea, vomiting, hypoglycaemia, hyperpyrexia, non-cardiogenic pulmonary oedema, coma

Question 6

Explain how you would manage aspirin overdose

Answer 6

o If there is metabolic acidosis or levels >500g/L = give sodium bicarbonate (50-100mmol), aim urine pH to be 7.5-8.5 and blood pH <7.55
o If levels are >700mg/L OR there is coma, seizures, pulmonary oedema or renal failure , consider haemodialysis

Question 7

Describe how TCA overdose may present

Answer 7

o Anti-muscarinic: confusion, agitation, dry skin, hyperthermia, thirst, dry mouth, tachycardia, urinary retention
o Sodium channel blockade: broad QRS, arrhythmia (any)
o CNS effects: confusion, delirium, seizures, myoclonus

Question 8

Explain the management of TCA (amitriptyline) overdose

Answer 8

If acidotic or QRS is widening – give IV sodium bicarbonate

Question 9

What’s the toxic dose of paracetamol?

Answer 9

Toxic dose: normally >150mg/kg in 24hr

Question 10

Explain the management of paracetamol overdose

Answer 10

> 0-8hrs after ingestion - measure paracetamol level as soon after 4hr post-ingestion, if above nomogram give full treatment of acetyl-cysteine
8-24hrs later - give full treatment of N-acetylcysteine and stop if below treatment line after measuring levels
>24hrs - give full treatment of N-acetylcysteine if jaundiced or have liver tenderness otherwise monitor
If paracetamol overdose was staggered over 1 hour, give full treatment

Question 11

How does N-acetylcysteine work in the treatment of paracetamol overdose?

Answer 11

Replenishing the body stores of the antioxidant glutathione. This then reacts with the toxic NAPQI metabolite from paracetamol so that it doesn’t damage cells and can be safely excreted.

Question 12

Explain the management of beta blocker overdose

Answer 12

> Give atropine (treat bradycardia)

> Glucagon (treat hypoglycaemia)