Acetylcysteine Injection - Antidote for Acetaminophen Overdose | Uses, Dosage, and Safety

Acetylcysteine Injection is an intravenous medication used to prevent or reduce liver damage caused by an overdose of acetaminophen in adults and children weighing 5 kg or more. It acts as an antidote to acetaminophen toxicity when administered promptly after overdose, especially within the first 8 hours of ingestion.

This medication is indicated to prevent or lessen hepatic injury after ingestion of potentially toxic amounts of acetaminophen in both adults and pediatric patients weighing at least 5 kg. It is used for acute overdoses and repeated supratherapeutic ingestion (RSI) scenarios with appropriate medical assessment.

Acetylcysteine

Acetylcysteine works by replenishing glutathione levels in the liver, which helps detoxify harmful metabolites produced by acetaminophen overdose. This detoxification process protects liver cells from injury and supports recovery.

General Administration

Acetylcysteine is given only by intravenous infusion and must be diluted properly prior to administration due to its high osmolarity (approximately 2,600 mOsmol/L). Preferred diluents include 0.45% sodium chloride injection, sterile water for injection, or 5% dextrose in water, with 0.45% sodium chloride generally preferred for better osmolarity and fluid balance.

Pre-Treatment Assessment

• Confirm timing and history of acetaminophen ingestion.
• Obtain plasma or serum acetaminophen concentration at least 4 hours after ingestion for guidance.
• Perform laboratory tests to monitor liver and kidney function and electrolyte balance.
• If timing is unknown or concentration unavailable within 8 hours, start treatment immediately.

Dosing Regimens

Total dose is 300 mg/kg, administered intravenously as either a three-bag or two-bag regimen:

• Loading dose: 150 mg/kg over 1 hour
• Second dose: 50 mg/kg over 4 hours
• Third dose: 100 mg/kg over 16 hours

Dosing volumes vary based on patient weight; consult tables for exact volumes.

• Loading dose: 200 mg/kg over 4 hours
• Second dose: 100 mg/kg over 16 hours

Two-bag regimen may have fewer hypersensitivity reactions; three-bag regimen preferred for patients ≤ 40 kg or with severe liver injury or large overdose.

Treatment Duration and Monitoring

• Complete the total infusion duration of 20–21 hours depending on regimen.
• If acetaminophen or liver function tests remain abnormal at treatment end, consider extending therapy following specialist advice.
• Monitor hepatic and renal function, electrolytes throughout treatment.

Important Safety Information

• Initiate treatment as soon as possible after overdose for maximal liver protection; efficacy decreases after 8 hours but treatment should not be withheld.
• Use clinical judgment and the Rumack-Matthew nomogram to guide therapy; some populations (e.g., chronic alcoholics, malnourished patients, or those on CYP2E1 inducers) may require treatment even if blood levels are below standard toxic thresholds.
• Carefully monitor for hypersensitivity reactions during infusion.
• Use appropriate diluent to avoid fluid overload or electrolyte imbalance; 0.45% sodium chloride is usually preferred.
• Exercise caution and consider extended treatment in massive overdose, delayed presentation, co-ingestion of other substances, or preexisting liver disease.

No specific drug interactions are detailed in the provided information. However, patients taking CYP2E1 enzyme inducers (e.g., isoniazid) may have increased acetaminophen toxicity risk, warranting careful monitoring and possible treatment with Acetylcysteine Injection even at lower acetaminophen levels.

Manifestations of acetylcysteine overdose are not described. Acetylcysteine Injection is used as an antidote for acetaminophen overdose; management focuses on monitoring liver function and clinical status during therapy.

After dilution, inspect solution for particulate matter or discoloration (color change to slight pink or purple is acceptable). The diluted solution can be stored at room temperature for up to 24 hours. Any unused portion of opened vials should be discarded and not reused.