Stages of acute acetaminophen intoxication

Stage	Hours after ingestion	Clinical features
I	0.5 to 24 hours	Nausea, vomiting, diaphoresis, pallor, lethargy, and malaise
		Some patients remain asymptomatic
		Laboratory studies are typically normal
II	24 to 72 hours	Stage I symptoms resolve
		Hepatotoxicity and nephrotoxicity become evident
		Right upper quadrant pain, liver enlargement and tenderness
		Elevation of aminotransferases occurs within 36 hours of ingestion in patients with hepatic injury
		Elevation of prothrombin time (PT) and internationalized ratio of PT
		Oliguria, abnormalities of renal function
		Elevation of serum amylase with or without clinical pancreatitis may occur
III	72 to 96 hours	Liver enzyme and function abnormalities peak (enzymes may be >10,000 IU/L)
		Recurrence of Stage I symptoms
		Jaundice, hepatic encephalopathy, hyperammonemia, bleeding diathesis, hypoglycemia, lactic acidosis
		Renal failure, the incidence of which is related to the severity of intoxication
		Death, from multi-organ failure, occurs most commonly in this stage
IV	4 to 14 days	Recovery phase
		Symptoms and laboratory values may not normalize for several weeks
		Histologic recovery lags behind clinical recovery and may take up to three months

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