What is the dose of Acetylcysteine (ACC) for a short course in an adult patient with no underlying medical conditions?

Acetylcysteine Dosing for Acetaminophen Overdose in Adults

For acute acetaminophen overdose in adults, 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

Loading Dose Administration

• Give 140 mg/kg as the initial loading dose using the 20% acetylcysteine solution diluted to 5% concentration 1
• Dilute the 20% solution with diet cola or other diet soft drinks to achieve a final concentration of 5% 1
• If administering via gastric tube or Miller-Abbott tube, water may be used as the diluent instead 1
• Prepare dilutions freshly and use within one hour of preparation 1

Maintenance Dosing

• Administer 70 mg/kg every 4 hours for 17 additional doses after the loading dose 1
• This provides a total treatment duration of 72 hours (18 total doses including the loading dose) 1
• Each maintenance dose is exactly half the loading dose 1

Practical Dosing Examples by Weight

For a 70 kg adult:

• Loading dose: 9,800 mg (49 mL of 20% solution diluted to 196 mL total volume) 1
• Maintenance dose: 4,900 mg (24.5 mL of 20% solution diluted to 98 mL total volume) 1

For an 80 kg adult:

• Loading dose: 11,200 mg (56 mL of 20% solution diluted to 224 mL total volume) 1
• Maintenance dose: 5,600 mg (28 mL of 20% solution diluted to 112 mL total volume) 1

Critical Timing Considerations

• Begin treatment immediately if acetaminophen overdose is suspected—do not wait for plasma level results 1
• Plasma acetaminophen concentrations should be obtained as early as possible, but no sooner than 4 hours post-ingestion, to assess hepatotoxicity risk 1
• If assay results are unavailable, assume the overdose is potentially toxic and initiate treatment 1

When to Continue or Discontinue Treatment

• Continue all 17 maintenance doses if the pre-treatment plasma level is above the treatment line (the broken line on the Rumack-Matthew nomogram, positioned 25% below the toxicity threshold) 1
• The treatment line connects 150 µg/mL at 4 hours with 37.5 µg/mL at 12 hours 1
• Discontinue treatment if the plasma level is below the treatment line, as hepatotoxicity risk is minimal 1

High-Risk Ingestions (Concentrations >300 mg/L at 4 Hours)

While some experts have proposed higher acetylcysteine doses for massive overdoses with concentrations exceeding 300 mg/L (1,985 μmol/L) at 4 hours 2, recent evidence shows no benefit and possible harm from high-dose regimens when treatment is delayed beyond 8 hours 3. The standard 300 mg/kg over 21 hours regimen remains appropriate even for high-risk ingestions, provided treatment begins promptly 3.

Common Pitfalls to Avoid

• Do not use enteric-coated formulations or parenteral solutions for oral administration—only the oral solution is approved for this route 1
• Do not reduce the proportion of diluent (always maintain 3 mL diluent per 1 mL of 20% acetylcysteine) 1
• Activated charcoal may adsorb up to 96% of acetylcysteine, potentially interfering with absorption 4
• Nausea, vomiting, and diarrhea are frequently reported side effects but rarely require treatment discontinuation 4
• Store opened vials in the refrigerator and use within 96 hours 1

Alternative Route

If the patient cannot tolerate oral administration due to severe nausea or vomiting, intravenous acetylcysteine is the preferred alternative (not covered in the oral dosing guidelines provided), though the oral solution described here is specifically not approved for parenteral injection 1.