Therapeutic Handbook - GGC Prescribing

Drug Overdose and ToxicityManagement of paracetamol overdose continued8 - 24 hours after ingestion• Send for urgent paracetamol plasma level. If the dose ingested is suspected to be > 150 mg/kgwithin 1 hour do not wait for result - commence treatment with acetylcysteine (dosing tablepage 40) immediately. The efficacy of acetylcysteine rapidly declines during this period so donot delay treatment.• For obese patients (> 110 kg) the toxic dose in mg/kg should be calculated using 110 kg, ratherthan patient’s actual weight.• Monitor blood results (details on previous page) and if results suggest acute liver injury thendouble check history of paracetamol ingestion, especially the timing. Consider treatment withacetylcysteine infusion – page 40.• Acetylcysteine can be discontinued if plasma paracetamol concentration is later reported to bebelow the treatment line on the graph on page 39, provided the patients is asymptomatic andLFTs, serum creatinine and INR are normal.> 24 hours after ingestion• A plasma concentration measured at this time is likely to be below the limit of detection, even aftera substantial overdose. Treat with acetylcysteine if > 24 hours after a suspected paracetamolingestion the:- measured concentration > 5mg/L at > 24 hours ingestion (indicative of a very largeoverdose) or- INR is normal (is < 1.3) but ALT > 2 times the upper limit of normal or- INR is > 1.3 (in the absence of any obvious cause) but ALT is normal (< 2 times the upperlimit of normal) or- the patient has jaundice or hepatic tenderness• For obese patients (> 110 kg) the toxic dose in mg/kg should be calculated using 110 kg, ratherthan patient’s actual weight.• Monitor blood tests (details on previous page) as well as venous or arterial blood gases.If INR or LFTs deranged then repeat bloods at 8 – 16 hours and consider other causes. Stopacetylcysteine if INR is < 1.3 and ALT has not increased further, otherwise continue and recheckbloods at 8 – 16 hour intervals.• For further management guidance refer to TOXBASE www.toxbase.org (password required) orcontact National Poisons Information Service (NPIS, 0844 892 0111).Staggered overdoses• Defined as paracetamol taken over > 1 hour.• Send for paracetamol levels and monitor blood tests (details on previous page). Note: Instaggered overdose the treatment nomogram is unreliable.• Clinically significant toxicity is unlikely if, following at least 24 hours since the last paracetamolingestion, the following criteria is met:- paracetamol measured concentration is not detectable (< 5 mg/L)- INR < 1.3- plasma creatinine normal- ALT < 2 times the upper limit of normal- patient asymptomatic Continues on next pagePage 38