Paracetamol overdose — nomogram and N-acetylcysteine

Assessment. Measure serum paracetamol in every deliberate self-poisoning patient regardless of stated dose. Use the Rumack–Matthew nomogram only for acute immediate-release ingestion with a known time; she qualifies at six hours. If the concentration would not be available by eight hours, start acetylcysteine while awaiting it.^[3]

Antidote. The ANZ two-bag regimen is acetylcysteine 200 mg/kg (maximum 22 g) intravenously over four hours, then 100 mg/kg (maximum 11 g) over 16 hours. At 60 kg, that is 12 g then 6 g. Adults use actual weight rounded up to the nearest 10 kg with a 110 kg ceiling.^[3]

Massive ingestion. If the initial concentration is more than double the nomogram line, double the second bag to 200 mg/kg over 16 hours. Discuss concentrations at or above triple the line with a clinical toxicologist or Poisons Information Centre.^[3]

Cessation. Repeat ALT two hours before completion. Continue if the concentration is above 10 mg/L or ALT is above 50 U/L and increasing. Beyond 20 hours, stop only when ALT or AST is decreasing, INR is below 2.0 and the patient is clinically well.^[3]