Paracetamol Overdose

 

Risk Factors for Hepatotoxicity

Certain groups are at an increased risk of developing liver toxicity following a paracetamol overdose:
i. Patients on Liver Enzyme-Inducing Drugs: Includes those taking medications like rifampicin, phenytoin, carbamazepine, or with chronic alcohol intake. These drugs increase liver metabolism, accelerating paracetamol’s conversion into toxic metabolites.
ii. Malnourished Patients: Those with conditions such as anorexia, bulimia, cystic fibrosis, hepatitis C, chronic alcoholism, or HIV, which may reduce glutathione reserves in the liver, making them more susceptible to toxicity.
iii. Patients with Prolonged Fasting: Lack of food intake depletes glutathione stores, increasing susceptibility to hepatotoxicity.

Initial Management on Admission

i. Baseline Investigations: Full blood count (FBC), urea and electrolytes (U&E), liver function tests (LFT), international normalized ratio (INR), blood gases, and glucose levels should be taken.
ii. Serum Paracetamol Level: Measure precisely 4 hours post-ingestion (not from admission time) to determine toxicity risk. This timing is crucial for accurate assessment.

 

Indications for IV N-Acetylcysteine Administration

N-Acetylcysteine is the antidote for paracetamol toxicity and should be administered if any of the following are present:
i. Staggered Overdose: Multiple doses taken over more than 1 hour, e.g., 6 grams daily for 5 days.
ii. Unknown Ingestion Time: If the time of ingestion is unclear, treatment should proceed regardless of plasma levels.
iii. Presentation >8 Hours After Ingestion: Immediate initiation of treatment is recommended.
iv. Signs of Liver Damage: Presence of jaundice or liver tenderness indicates potential hepatotoxicity.
v. Unconscious or Suspected Overdose: Administer N-Acetylcysteine even if the history is unclear.
vi. 4-Hour Plasma Paracetamol Concentration: If levels are on or above the treatment line at 4 hours post-ingestion, treatment should be initiated, regardless of risk factors.

Critical Points in Assessment and Follow-Up

i. If Patient Presents After Taking 30 Tablets or More: Measure paracetamol levels 4 hours post-ingestion (from ingestion time, not hospital arrival) before starting treatment with N-Acetylcysteine.
ii. If Serum Paracetamol Level is Normal: Refer the patient to the psychiatric team for evaluation, as no medical treatment is needed. This referral helps prevent future suicide attempts and addresses psychological concerns.

Note: The critical toxic dose of Paracetamol is 150 mg/kg within 24 hours.

Post-Treatment and Discharge
i. Medical Team Role: The medical team manages acute symptoms and N-Acetylcysteine administration.
ii. Psychiatric Referral Post-Discharge: Once medically stabilized, the patient should be referred to psychiatry to address underlying mental health issues and prevent recurrent overdose attempts.