Acetaminophen Overdose

Toxic dose: 150–200 mg/kg, but not to exceed 8–10 g (acute) or > 4 g/day (chronic)

Nausea, vomiting shortly after ingestion

Hepatic necrosis evident after 24–48 h

Nausea or vomiting shortly after ingestion

Hepatic aminotransferase levels begin to increase 24–48 after ingestion; there are usually no other signs of toxicity

With severe poisoning, fulminant hepatic necrosis may occur, resulting in

• Jaundice

• Hepatic encephalopathy

• Acute kidney injury

• Death

Rarely, massive ingestion (eg, serum levels over 500–1000 mg/L [33–66 mmol/L]) can cause

• Early onset of acute coma

• Seizures

• Hypotension

• Metabolic acidosis

The diagnosis after acute overdose is based on measurement of the serum acetaminophen level

Plot the serum level versus the time since ingestion on the acetaminophen nomogram shown in Figure 38–1

Ingestion of sustained-release products or coingestion of an anticholinergic agent, salicylate, or opioid drug may cause delayed elevation of serum levels which can make interpreting the nomogram difficult

The nomogram is not useful after chronic or staggered overdose

Oral activated charcoal (if given within 1–2 hours of acute ingestion)

Oral N-acetylcysteine (NAC), 140 mg/kg oral loading dose, followed by 70 mg/kg every 4 hours

Traditional US oral regimen 72 hours (17 doses), although equivalent success has been achieved with 20–48 hours of treatment

Intravenous NAC (Acetadote), 150 mg/kg administered over 60 minutes, then 50 mg/kg over 4 hours, then 100 mg/kg over 16 hour (21-hour infusion)

Treatment with N-acetylcysteine is most effective if it is started within 8–10 hours after ingestion

Hemodialysis is rarely indicated but might be needed in some patients with massive overdose