Nausea and vomiting
Previous anaphylactic reaction to Acetylcysteine
CAN be used during pregnancy
Patients at risk of liver damage and therefore requiring treatment can be identified from a single measurement of the plasma-paracetamol concentration, related to the time from ingestion, provided this time interval is not less than 4 hours; earlier samples may be misleading. The concentration is plotted on a paracetamol treatment graph of a reference line (‘normal treatment line') joining plots of 200 mg/litre (1.32 mmol/litre) at 4 hours and 6.25 mg/litre (0.04 mmol/litre) at 24 hours (see Paracetamol poisoning treatment graph). Those whose plasma-paracetamol concentration is above the normal treatment line are treated with acetylcysteine by intravenous infusion (or, if acetylcysteine is not available, with methionine by mouth, provided the overdose has been taken within 10–12 hours and the patient is not vomiting).
Patients on enzyme-inducing drugs (e.g. carbamazepine, phenobarbital, phenytoin, primidone, rifampicin, alcohol, and St John’s wort) or who are malnourished (e.g. in anorexia, in alcoholism, or those who are HIV-positive) may develop toxicity at lower plasma-paracetamol concentration and should be treated if the concentration is above the high-risk treatment line (which joins plots that are at 50% of the plasma-paracetamol concentrations of the normal treatment line).
The prognostic accuracy of plasma-paracetamol concentration taken after 15 hours is uncertain but a concentration above the relevant treatment line should be regarded as carrying a serious risk of liver damage.
Plasma-paracetamol concentration may be difficult to interpret when paracetamol has been ingested over several hours. If there is doubt about timing or the need for treatment then the patient should be treated with an antidote.
By intravenous infusion, adult and child, initially 150 mg/kg over 15 minutes, then 50 mg/kg over 4 hours then 100 mg/kg over 16 hours
Dilute requisite dose in glucose intravenous infusion 5% as follows: adult and child over 12 years, initially 200 mL given over 15 minutes, then 500 mL over 4 hours, then 1 litre over 16 hours; child under 12 years body-weight over 20 kg, initially 100 mL given over 15 minutes, then 250 mL over 4 hours, then 500 mL over 16 hours; child body-weight under 20 kg, initially 3 mL/kg given over 15 minutes, then 7 mL/kg over 4 hours, then 14 mL/kg over 16 hours
Manufacturer also recommends other infusion fluids, but glucose 5% is preferable