What is the dose of acetylcysteine (N-acetylcysteine) for a short course in an adult with normal renal function?

Acetylcysteine Dosing for Short Course in Adults

For acetaminophen overdose, administer a loading dose of 140 mg/kg orally, followed by 70 mg/kg every 4 hours for 17 additional doses (total 72 hours of treatment). 1

Acetaminophen Overdose Protocol

Loading Dose

• 140 mg/kg orally as the initial dose 1
• Dilute the 20% acetylcysteine solution to a final concentration of 5% using diet cola or other diet soft drinks 1
• If administering via gastric tube, water may be used as the diluent 1
• Freshly prepared dilutions should be used within one hour 1

Maintenance Dosing

• 70 mg/kg orally every 4 hours for 17 additional doses 1
• This provides a total treatment duration of 72 hours (18 total doses including the loading dose) 1

Practical Dosing Examples by Weight

For a 70 kg adult:

• Loading dose: 9.8 grams (49 mL of 20% solution diluted to 196 mL total volume) 1
• Maintenance dose: 4.9 grams (24.5 mL of 20% solution diluted to 98 mL total volume) every 4 hours 1

Alternative Indication: Contrast-Induced Nephropathy Prevention

Standard Oral Dosing

• 600 mg orally twice daily starting 24 hours before contrast exposure and continuing the day of the procedure 2
• This regimen has been studied primarily with low-dose contrast agents 2

Higher-Dose Oral Regimen

• 1200 mg orally twice daily for 2 days, starting the day before contrast exposure 3, 2
• The double-dose regimen (1200 mg twice daily) was significantly more effective than standard dosing when high volumes of contrast (≥140 mL) were used, reducing nephrotoxicity from 11% to 3.5% 2
• However, with moderate to high contrast doses (>1 cc/kg), oral acetylcysteine at 600 mg twice daily showed no benefit over hydration alone 4

Intravenous Dosing for Contrast Nephropathy Prevention

• 450 mg/kg IV has been established as the maximum tolerated dose in adults with renal impairment 5
• Alternative IV regimen studied: 50 mg/kg/hour for 2 hours before contrast, then 20 mg/kg/hour for 5 hours 3

Methemoglobinemia Treatment

The role of N-acetylcysteine in methemoglobinemia is unclear and not standardized. 6

• N-acetylcysteine has been suggested as a cofactor to enhance methemoglobin reduction and increase intracellular glutathione 6
• It may be considered in patients with methemoglobinemia and G6PD deficiency, or acetaminophen-induced methemoglobinemia 6
• No standardized dosing exists for this indication 6

Important Clinical Considerations

Preparation and Storage

• Unopened vials of 20% acetylcysteine solution can be stored in the refrigerator for up to 96 hours after opening 1
• Never administer acetylcysteine solution parenterally—it is not approved for parenteral injection 1

Common Pitfalls

• Do not wait for acetaminophen assay results before initiating treatment—begin acetylcysteine immediately if overdose is suspected 1
• Activated charcoal may interfere with oral acetylcysteine absorption, adsorbing up to 96% of the drug 7
• Nausea, vomiting, and diarrhea are frequently reported side effects 7
• The terminal half-life of oral acetylcysteine is 6.25 hours, with peak plasma concentrations of 0.35-4 mg/L achieved within 1-2 hours 7

Renal Function Considerations

• Approximately 70% of total body clearance is nonrenal, with renal clearance of 0.190-0.211 L/h/kg 7
• No dose adjustment is required for renal impairment when using acetylcysteine for acetaminophen overdose 1