Key investigations

Key investigations for modified-release paracetamol poisoning include:

• serum paracetamol concentration—measure every 4 to 6 hours to check for ongoing paracetamol absorption
• serum alanine aminotransferase (ALT) concentration—to guide appropriate acetylcysteine therapy.

Serum ALT concentration rises slowly after an acute ingestion of modified-release paracetamol, and may remain within the reference range for 24 hours or longer.

Other investigations that may be performed if the serum ALT concentration is abnormal include:

• blood glucose concentration
• serum electrolyte, urea and creatinine concentrations
• INR
• blood gas analysis.