What is the treatment for a patient with a stable vital signs who ingested 6.5g of paracetamol (acetaminophen)?

Treatment for Paracetamol (Acetaminophen) Overdose of 6.5g

N-acetylcysteine (NAC) should be administered immediately to this patient with 6.5g paracetamol ingestion, even with stable vital signs, as early treatment significantly reduces the risk of hepatotoxicity and mortality. 1, 2

Initial Assessment and Management

• Obtain serum acetaminophen level as soon as possible, but no sooner than 4 hours post-ingestion to accurately assess potential toxicity using the Rumack-Matthew nomogram 2, 3
• If the patient presented within 4 hours of ingestion, administer activated charcoal (1g/kg orally) prior to starting NAC therapy 2, 3
• Do not wait for acetaminophen level results before initiating NAC treatment if the history suggests a potentially toxic ingestion 3, 2
• Draw baseline liver function tests including SGOT (AST), SGPT (ALT), bilirubin, prothrombin time, creatinine, BUN, blood sugar, and electrolytes 3, 1

NAC Administration Protocol

• Administer oral NAC with a loading dose of 140 mg/kg followed by maintenance doses of 70 mg/kg every 4 hours 3, 2
• For oral administration, dilute the 20% NAC solution with diet cola or other soft drinks to a final concentration of 5% 3
• If the patient cannot tolerate oral NAC due to vomiting, consider intravenous administration (loading dose 150 mg/kg in 5% dextrose over 15 minutes; maintenance dose 50 mg/kg over 4 hours followed by 100 mg/kg over 16 hours) 1
• If vomiting occurs within 1 hour of oral dose administration, repeat that dose 3

Risk Assessment and Treatment Duration

• Plot the acetaminophen level on the Rumack-Matthew nomogram to determine risk category (probable risk, possible risk, or no risk) 1
• Continue NAC treatment if the acetaminophen level is above the "possible risk" line on the nomogram 3, 2
• Early initiation of NAC is critical - treatment within 8 hours is associated with only 2.9% risk of severe hepatotoxicity, while delay beyond 10 hours increases this risk to 26.4% 1, 2
• For a 6.5g ingestion (which is below the typical 10g threshold for severe toxicity but still potentially harmful), continue NAC until acetaminophen levels are undetectable and liver enzymes are normal 2, 4

Monitoring During Treatment

• Monitor liver function tests daily if the acetaminophen level is in the potentially toxic range 3, 1
• Watch for signs of NAC-related adverse effects, particularly anaphylactoid reactions with IV administration (nausea, vomiting, flushing, urticaria, bronchospasm) 1, 5
• For patients with persistent vomiting, consider duodenal intubation for NAC administration or switch to IV formulation 3

Special Considerations

• Even though 6.5g is below the typical 10g threshold associated with severe hepatotoxicity in most adults, individual susceptibility varies and some patients have developed severe liver injury with doses as low as 3-4g/day 1, 2
• Risk factors for increased susceptibility include chronic alcohol use, malnutrition, and use of enzyme-inducing medications 2, 6
• If the patient has elevated baseline liver enzymes, they may be at higher risk and should be monitored more closely 6, 2

Common Pitfalls to Avoid

• Do not delay NAC administration while waiting for acetaminophen levels if the history suggests a potentially toxic ingestion 3, 2
• Do not rely solely on the patient's reported ingestion amount, as histories are often unreliable 3, 5
• Do not discontinue NAC prematurely - treatment should continue until acetaminophen levels are undetectable and liver enzymes are normal 4, 2
• Do not administer activated charcoal after NAC has been given orally, as it may adsorb the antidote and reduce its effectiveness 3, 2