This Acetaminophen overdose with NAC dosing calculator establishes the Acetylcysteine dosing to avoid overdose hepatic risk of paracetamol and similar drugs. Below the form you can read more on the usage of Acetadote and the clinical guidelines.

Route of NAC (N-Acetylcysteine)*

How does this Acetaminophen overdose with NAC dosing calculator work?

This is a health tool that determines the N-acetylcysteine dosage for patients who have just ingested a high dosage of Paracetamol or Tylenol or other medication containing acetaminophen.

This Acetaminophen overdose with NAC dosing calculator follows the clinical recommendation and management of this kind of overdose and suggests the dosage treatment with acetadote or NAC (N-acetylcysteine or N-acetyl-L-cysteine) within 8 hours post-ingestion to decrease the risk of hepatotoxicity, exemplified by AST or ALT levels higher than 1000 IU/L. The early start of the treatment is essential in order to prevent liver damage.

For easefulness, the dosage is either oral or intravenous and the user can select either of the methods before inputting the patient weight in kg or lbs.

Acetaminophen toxicity is often plotted on the Rumack-Matthew nomogram but this can only be done if the clinician can establish an exact time of ingestion and only starting 4 hours after ingestion in order to confirm toxicity not simply exposure. The nomogram represents a toxicology tool aiming to predict the outcome of patients with acetaminophen dosage and the risk of hepatotoxicity after high intake. The Rumack study from 1981 assesses the effectiveness of NAC dosing in preventing hepatotoxicity and established the first guidelines.

Although not a very known fact, acetaminophen (Tylenol, Paracetamol etc.) overdose is one of the most common poisonings as this kind of pain medication is considered by the general public as safe and people often superimpose doses without respecting the normal recommended half times of the medication.

Acetylcysteine is a generic medication, used to treat paracetamol overdose by binding with the toxic break products but is also used in chronic obstructive pulmonary disease and can be administered by mouth, intravenous or inhaled. It is also on the World Health Organization's List of Essential Medicines, therefore the treatment is facilitated in most medical units. It is often found in combination with other agents such as diphenhydramine or dextromethorphan.

NAC therapy is contraindicated in patients who are hypersensitive or presented a previous anaphylactoid reaction and also in patients with asthma or a history of bronchospasm.

Common side effects of acetadote include nausea and vomiting, redness of the skin, urticaria and pruritus and sometimes some anaphylaxis processed might start, although not with an immune component.

NAC dosing PO and IV

Oral administration starts with a loading dose of 140 mg/kg than every 4 hours another 17 more doses of 70 mg/kg. Given the administration way, in case one of the adverse effects, vomiting is present within one hour of dose ingestion, the dose should be repeated.

In regard to intravenous administration, the following table presents the three doses according to patient weight and explains the break down of them:

  ≤20 kg (20 – 40 kg) ≥40 kg
Loading dose 150 mg/kg in 3 mL/kg diluent (60 min) 150 mg/kg in 100 mL diluent (60 min) 150 mg/kg in 200 mL diluent (60 min)
Dose II 50 mg/kg in 7 mL/kg diluent (4 hr) 50 mg/kg in 250 mL diluent (4 hr) 50 mg/kg in 500 mL diluent (4 hr)
Dose III 100 mg/kg in 14 mL/kg diluent (16 hr) 100 mg/kg in 500 mL diluent (16 hr) 100 mg/kg in 1000 mL diluent (16 hr)

In case the patient condition restricts fluids the quantity of diluents should be adapted. In general the diluents of choice are 5% dextrose (D5W) or ½ normal saline.


1) Rumack BH, Peterson RC, Koch GG, Amara IA. (1981) Acetaminophen overdose. 662 cases with evaluation of oral acetylcysteine treatment. Arch Intern Med; 141(3 Spec No):380-5.

2) Prescott LF, Illingworth RN, Critchley JA, Stewart MJ, Adam RD, Proudfoot AT. (1979) Intravenous N-acetylcystine: the treatment of choice for paracetamol poisoning. Br Med J; 2(6198):1097-100.

3) Smilkstein MJ, Knapp GL, Kulig KW, Rumack BH. (1988) Efficacy of oral N-acetylcysteine in the treatment of acetaminophen overdose. Analysis of the national multicenter study (1976 to 1985) N Engl J Med; 319(24):1557-62.

18 Oct, 2015