Paracetamol Overdose

Presentation

People who have ingested paracetamol are frequently asymptomatic - symptoms are unreliable

Non-specific symptoms for drug overdoses include:

  • Nausea and vomiting
  • Pain
  • Trouble with breathing
  • Seizures
  • Confusion
  • Abnormal skin colour

History

  • Ascertain the age, weight, and sex
  • Use information from friends, family members, or other health professionals to help determine the exact circumstances of the overdose
  • What was taken?
  • How much was taken?
  • When was it taken?
  • What was the route of administration? Oral, inhalation, or injection?
  • Why was the substance taken - accidental or deliberate? People who have self harmed will need a further psychosocial assessment after treatment of physical problems
  • Past medical history that will affect the excretion or metabolism of the poison
    • Renal or hepatic impairment
    • Low glutathione reserves due to HIV-positive status, malnutrition, alcohol-related or other liver disease
  • Ask for the container or a sample of the medication if possible
  • Drug history - Increased toxicity in patients taking rifampicin, phenobarbital, phenytoin, carbamazepine and alcohol (due to induction of the P450 system)

Vital signs / observations

Blood Pressure
Respiratory rate
HR

Examination

Usually few findings unless the patient develops acute hepatic failure
<24 hours of ingestion: abdominal tenderness usually in the epigastrium or right upper quadrant

Bedside tests

U&Es and creatinine - assess renal impairment
LFTs - assess hepatotoxitcy as ALT can rise to >1000 IU/L
Clotting screen: prothrombin time is the best indicator of severity of liver failure and the INR should be checked 12-hourly
Glucose: hypoglycaemia is common in hepatic necrosis
ABG - assess for acidosis

Laboratory investigations

Plasma paracetamol measured no earlier than 4 hours and no later than 15 hours after ingestion, as results are not reliable outside this time period.

Differential diagnosis

  • Head trauma (especially due to alcohol intoxication).
  • Stroke/subarachnoid haemorrhage
  • Meningitis
  • Metabolic abnormalities (such as hypoglycaemia, hyponatraemia, or hypoxaemia).
  • Liver disease
  • Post-ictal state

Initial Management

Resucitate if necessary using the ABC approach

  • Sedative medication if the person is agitated
  • Ventilation if the person stops breathing
  • Antiepileptic medication if seizures develop

Ingestion <4 hours ago

Oral activated charcoal (50g) if:

  • patient presents within one hour of ingestion and
  • they have taken >150 mg/kg or 12 g in total

Then wait until 4hours post-ingestion to take plasma paracetamol levels
All patients with a timed plasma paracetamol level on or above a single treatment line joining points of 100mg/L at 4 hours and 15mg/L at 15 hours after ingestion should receive N-acetylcysteine
Treat patient with IV N-acetyl cysteine using a weight-based dosing table
If there is doubt about the timing of paractemol ingestion or risk of a staggered overdose, give N-acetylcysteine without delay

Ingestion 4-24 hours post ingestion

Start IV N-acetyl cysteine whilst waiting for results

Ingestion >24 hours ago

Paracetamol level is irrelevant at this stage as it will all have been excreted or metabolised

Prognosis

Discuss risk of repeat self-poisoning
Nausea and vomiting usually settle within 24 hours

Complications

Persistent nausea and vomiting with right subcostal pain suggests hepatic necrosis which may lead to encephalopathy, hypoglycaemia, haemorrhage, cerebral oedema and death.

King's College Hospital criteria for hepatic transplantation

Arterial pH < 7.3, 24 hours after ingestion

or all of:

  • prothrombin time > 100 seconds
  • creatinine > 300 umol/l
  • grade III or IV encephalopathy
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