Paracetamol Poisoning

Description

Diagnostic criteria

Medicine treatment

Referral

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ICD-10 code: T39.1

DESCRIPTION

Poisoning due to paracetamol by adolescents is generally due to intentional ingestion. The accidental ingestion of paracetamol elixir preparations by toddlers very rarely causes toxicity. Toxicity can be due to acute ingestions or repeated supratherapeutic ingestion (RSTI). Toxicity due to IV paracetamol may also occur.

Patients with predisposing risk factors for hepatotoxicity, so-called ‘high-risk’ patients (glutathione deficiency, liver disease, use of enzyme- inducing drugs, patients with recent illness or dehydration) may experience toxicity at lower doses.

DIAGNOSTIC CRITERIA

• An acute ingestion in excess of 200 mg/kg per 24-hour period in healthy children is potentially toxic.
• Serum paracetamol concentration must be measured at least four hours following ingestion.
• Use nomogram to assess risk of toxicity.

Click on image to enlarge

• Cautions for use of this chart:
  • The time co-ordinates refer to time since ingestion.
  • Serum levels drawn before 4 hours may not represent peak levels.
  • Use the graph only in relation to a single acute ingestion.
  • Do not use when there is a history of RSTI, or delayed presentation (> 24 hours post-ingestion).

Repeated supratherapeutic ingestions (RSTI)

Can occur with repeated high doses of the same product or the concurrent use of multiple paracetamol-containing products.

RSTI is defined as:

• >200 mg/kg or 10 g (whichever is less) over a single 24-hour period.
• >150 mg/kg or 6 g (whichever is less) per 24-hour period for the preceding 48 hours.
• > 100 mg/kg or 4 g/day (whichever is less) per 24-hour period for more than 48 hours AND patients with symptoms suggestive of liver injury.

This nomogram is not designed for use in RSTI. Management of RSTI is complex; contact the Poisons Information Helpline for advice.

LoE III⁸

Investigations
If toxic dose ingested or patient symptomatic, do:

• Serum paracetamol level.
• Baseline electrolytes.
• ALT.
• INR, if abnormal ALT or showing signs of hepatotoxicity.

MEDICINE TREATMENT

Acute ingestion:

• Gastric lavage is unlikely to be required.
• Activated charcoal can be considered for large intentional overdoses.
• For acute ingestion, initiate treatment with N-acetyl cysteine (NAC) if the blood paracetamol concentration for the time since ingestion falls to the right of the curved line on the nomogram.
• If a patient has taken a potentially toxic dose [≥ 10 g (20 tablets) or ≥ 200 mg/kg, whichever is smaller] AND the serum paracetamol level results will not be available before 8 hours post-ingestion OR the patient presents > 8 hours post-ingestion, do not delay initiation of NAC. It can always be stopped if the serum level plotted on the nomogram does not indicate its continued use.
• If the time of ingestion is unknown, start treatment for any detectable level of paracetamol or any elevation of AST or ALT.

RSTI:

Management of RSTI is complex; contact the Poisons Information Helpline for advice.

• N-Acetylcysteine, IV:
  20-hour regimen:
  • 200 mg/kg in 7 mL/kg of 5% dextrose over 4 hours.
  • Followed by 100 mg/kg in 14 mL/kg 5% dextrose over 16 hours.

Repeat infusions according to second dose.

REFERRAL

Patients with severe hepatotoxicity as indicated by any of the following:

• INR > 2 IU at 24 hours or > 3 IU at any time after overdose,
• pH < 7.3, bicarbonate < 18 mmol/L or lactate > 3 mmol/L,
• hypotension despite adequate fluid resuscitation,
• encephalopathy,
• creatinine > 200 µmol/L.

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Standard Treatment Guidelines and Essential Medicines List for South Africa, Hospital Level, Paediatrics, 2023 Edition

Chapter 18: Poisoning,  18.1 Poisoning, 18.1.11 Paracetamol Poisoning