Acetaminophen overdose associated with double serum concentration peaks.

Area of Science:

• Toxicology
• Pharmacology
• Hepatology

Background:

• Acetaminophen overdose is a leading cause of drug-induced liver injury.
• N-acetylcysteine (NAC) is the standard antidote for acetaminophen poisoning.
• Optimal duration of NAC therapy remains debated, particularly in complex cases.

Observation:

• A 65-year-old male with acetaminophen and opioid co-ingestion exhibited a second peak in acetaminophen serum levels after completing the standard 21-hour NAC protocol.
• This delayed absorption phenomenon occurred despite achieving standard criteria for drug level monitoring.

Findings:

• Prolonging NAC infusion beyond the standard protocol, even after a treatment gap, was essential to prevent hepatotoxicity in this case.
• Delayed acetaminophen absorption, potentially exacerbated by opioid co-ingestion, can lead to a secondary rise in serum concentrations.

Implications:

• Patients with acetaminophen toxicity and risk factors for delayed gastric emptying (e.g., opioid co-ingestion) require extended NAC therapy and vigilant monitoring.
• Continuous monitoring of aminotransferase levels and serial acetaminophen concentrations until undetectable is recommended before discontinuing NAC.
• This case highlights the importance of individualized treatment duration for NAC based on patient-specific factors and drug absorption patterns.