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Antidotes, Systemic
Miscellaneous Dietary Supplements
Supplemental Dietary Agents


For storage information, see specific product information within the How Supplied section.

Oral Administration Oral Liquid Formulations

Oral solution (Mucomyst):
Oral acetylcysteine has very poor taste and a strong sulfur-like odor. Diluting the solution with a very cold beverage (e.g., soda, orange juice), serving in a cup with a lid, and drinking the solution through a straw may help to increase palatability and lower the risk of vomiting.
Dilution of 10% solution: 1 mL of diluent for every 1 mL of solution.
Dilution of 20% solution: 3 mL of diluent for every 1 mL of solution.
If the patient cannot drink, the solution may be administered via a nasogastric tube.
Use diluted solutions within 1 hour of preparation.
If the patient vomits within 1 hour of administration, repeat dose.
Storage: Remaining undiluted solutions in opened vials can be stored in the refrigerator up to 96 hours.

Injectable Administration

Visually inspect parenteral products for particulate matter and discoloration prior to administration whenever solution and container permit.The color of the IV formulation may turn from colorless to a slight pink or purple color after the stopper is punctured; however, the quality of the product is not affected.

Intravenous Administration

The IV formulation is hyperosmolar (2,600 mOsm/L) and must be diluted prior to administration.
Compatible diluents include: 5% Dextrose Injection, 0.45% Sodium Chloride Injection, and Sterile Water for Injection. If Sterile Water for Injection is used, carefully consider the osmolarity of the resultant solution; some concentrations would be too hypo-osmolar for safe administration (see osmolarity content below).
For the 3-bag regimen, the standard volume of diluent to be used is dependent on patient weight as follows:
Patients weighing 41 kg or more:
Loading dose: dilute in 200 mL diluent
Second dose: dilute in 500 mL diluent
Third dose: dilute in 1,000 mL diluent
Patients weighing 21 to 40 kg:
Loading dose: dilute in 100 mL diluent
Second dose: dilute in 250 mL diluent
Third dose: dilute in 500 mL diluent
Patients weighing 5 to 20 kg:
Loading dose: dilute in 3 mL/kg diluent
Second dose: dilute in 7 mL/kg diluent
Third dose: dilute in 14 mL/kg diluent
For the 1-bag regimen, dilute 30 g of acetylcysteine in 1 L of 5% Dextrose Injection.
For patients requiring fluid restriction, reduce the dilution volume as clinically appropriate; however, carefully consider the osmolarity of the resultant solution and avoid infusion of a hyper- or hypo-osmolar solution.
Acetylcysteine diluted to a concentration of 7 mg/mL
Osmolarity in 0.45% Sodium Chloride Injection: 245 mOsmol/L
Osmolarity in 5% Dextrose Injection: 343 mOsmol/L
Osmolarity in Sterile Water for Injection: 91 mOsmol/L (below recommended osmolarity for administration)
Acetylcysteine diluted to a concentration of 24 mg/mL
Osmolarity in 0.45% Sodium Chloride Injection: 466 mOsmol/L
Osmolarity in 5% Dextrose Injection: 564 mOsmol/L
Osmolarity in Sterile Water for Injection: 312 mOsmol/L
The manufacturer provides a Dosage Guide and Preparation Chart in relation to body weight in the product label.
Storage: The commercially available vials are intended for single-dose use and are preservative-free. Diluted solutions are stable for 24 hours at controlled room temperature.
IV Infusion
Administer the portions of a multi-bag or multi-step regimen sequentially as a continuous infusion with no significant time between doses.
Acetylcysteine reacts with certain materials (e.g., iron, nickel, copper, rubber); any part of the IV equipment that comes in contact with acetylcysteine should be made of plastic or glass.

Inhalation Administration

Solutions may be given via nebulization into a face mask, mouth piece, tracheostomy, tent, or croupette; direct instillation intratracheally is also FDA-approved.
The 10% solution may be administered undiluted.
The 20% solution may be administered undiluted or, if desired, may be diluted in 0.9% Sodium Chloride Injection or Sterile Water for Injection or Inhalation.
Most commercially available nebulizers will produce appropriate particle sizes; however, hand bulbs and some hand-operated nebulizers are not recommended for routine use nebulizing acetylcysteine.
Do not place acetylcysteine directly into the chamber of a heated nebulizer.
For prolonged nebulizations, when 75% of the initial volume of acetylcysteine has been nebulized, a quantity of Sterile Water for Injection approximately equal to the remaining acetylcysteine volume should be added to the nebulizer.
Acetylcysteine reacts with certain materials (e.g., iron, nickel, copper, rubber); therefore, any part of the nebulizer equipment that comes in contact with acetylcysteine should be made of plastic or glass.
Storage: Opened vials may be stored in the refrigerator and used within 96 hours.

Other Administration Route(s)

Intratracheal Administration
Intratracheal instillation: Instill directly into the trachea or tracheostomy.
Percutaneous intratracheal catheter: Administer the solution via a syringe attached to the catheter.

Adverse Reactions

anaphylactoid reactions / Rapid / 7.9-17.0
bronchospasm / Rapid / Incidence not known


sinus tachycardia / Rapid / 3.0-5.0
edema / Delayed / 1.2-1.6
hypotension / Rapid / 0.1-0.1
erythema / Early / Incidence not known
dyspnea / Early / Incidence not known
stomatitis / Delayed / Incidence not known
hemoptysis / Delayed / Incidence not known
wheezing / Rapid / Incidence not known


urticaria / Rapid / 6.1-7.6
flushing / Rapid / 6.1-7.6
pruritus / Rapid / 4.1-4.3
rash / Early / Incidence not known
rhinorrhea / Early / Incidence not known
pharyngitis / Delayed / Incidence not known
nausea / Early / Incidence not known
vomiting / Early / Incidence not known
dysgeusia / Early / Incidence not known
drowsiness / Early / Incidence not known
fever / Early / Incidence not known

Common Brand Names

Acetadote, Mucomyst, Mucosil Acetylcysteine

Dea Class



N-acetyl derivative of L-cysteine, abbreviated as NAC; possesses a strong odor, often described as rotten eggs
Used orally or parenterally as an antidote for acetaminophen overdose to prevent hepatotoxicity
Used via inhalation as a mucolytic agent to treat and reduce COPD exacerbations

Dosing Considerations
Hepatic Impairment

Specific guidelines for dosage adjustments in hepatic impairment are not available; it is not known if dosage adjustments are needed. Although there was a 3-fold increase in acetylcysteine plasma concentrations in patients with hepatic cirrhosis, the published medical literature does not indicate that the dose of acetylcysteine in patients with hepatic impairment should be reduced.

Renal Impairment

Specific guidelines for dosage adjustments in renal impairment are not available. Some experts have recommended the following adjustment for adult patients receiving systemic therapy of 140 mg/kg load then 70 mg/kg every 4 hours x 17 doses :
CrCl 10 ml/minute or greater or CRRT: no dosage adjustment
CrCl less than 10 ml/minute or peritoneal dialysis: 75% of recommended dose

Drug Interactions

Charcoal: (Moderate) Administration of activated charcoal and oral acetylcysteine at the same time may cause a reduction in acetylcysteine (NAC) absorption. There are conflicting data as to whether the reduced bioavailability of NAC is clinically significant during the treatment of drug overdoses. In the case of a mixed drug overdose activated charcoal may be indicated for use along with NAC. However, if activated charcoal has been administered, lavage before administering oral NAC treatment. Activated charcoal adsorbs acetylcysteine in vitro and may do so in patients and thereby may reduce its effectiveness.

How Supplied

Acetadote/Acetylcysteine Intravenous Inj Sol: 1mL, 200mg
Acetylcysteine/Mucomyst/Mucosil Acetylcysteine Oral Sol: 10%
Acetylcysteine/Mucomyst/Mucosil Acetylcysteine Respiratory (Inhalation) Sol: 10%, 20%

Maximum Dosage

NOTE: Maximum dosage may vary based upon indication and route of administration. Specific maximum dosage information is not available; however, commonly used maximum doses for IV acetylcysteine are 150 mg/kg (Max: 15,000 mg) for the loading dose, 50 mg/kg (Max: 5000 mg) for the second dose, and 100 mg/kg (Max: 10,000 mg) for the third dose. Specific maximum dosage information is not available for oral or inhalational dosing.


Maximum dosage is not well defined.


Maximum dosage is not well defined.


Maximum dosage is not well defined.


Maximum dosage is not well defined.

Mechanism Of Action

Mechanism of Action:•Antioxidant effects: Antioxidants such as acetylcysteine may prevent tissue damage to various organs by scavenging oxygen free radicals (e.g., superoxides) or by other poorly understood mechanisms, such as stabilization of cellular signal transduction systems and reduced apoptosis (programmed cell death). Acetylcysteine enhances the effects of nitric oxide (NO) by combining with NO to form S-nitrosothiol, a potent and biologically stable vasodilator. Acetylcysteine may thus compete with the superoxide radical for NO and thus prevent the formation of a damaging perioxinitrite free-radical. Thus, acetylcysteine exhibits multiple potential mechanisms of action that may limit ischemia and promote cellular repair and survival. Studies using acetylcysteine as an antioxidant for organ protection in settings of clinically-relevant heart, lung, liver, and renal ischemia are intriguing and continue to be pursued.•Mucolytic effects: As a mucolytic, it is believed that the free sulfhydryl groups in acetylcysteine react with the disulfide linkages of mucoproteins in bronchial secretions. This, in turn, acts to decrease the hypersecretion and viscosity of mucus secretions of the lungs and aids in the removal of these secretions through coughing, mechanical mechanisms, or postural drainage. Acetylcysteine does not depolymerize proteins and has no action on fibrin or living cells. In COPD, the use of oral acetylcysteine may also promote reductions in bacterial cell counts within the sputum, thus contributing to reduced exacerbation rates.•Prevention of hepatotoxicity secondary to acetaminophen (APAP) overdose: As an antidote, acetylcysteine is used to prevent hepatotoxicity after an acute overdose of acetaminophen. In this role, the sulfhydryl groups of acetylcysteine serve as a substrate for the toxic acetaminophen metabolite in place of glutathione in the liver. It is believed that acetaminophen is hepatotoxic due to the depletion of these glutathione residues. For acetylcysteine to be effective, it must be administered within several hours after the acute ingestion. Benefits are primarily seen in patients treated within 8—10 hours of the overdose.•Proposed prevention of nitrate tolerance: Sulfhydryl groups are also believed to be important in the response to vasodilator nitrates used in the treatment of ischemic heart disease. It is well known that tolerance to nitrates occurs after prolonged use. One proposed mechanism, based on in vitro data, is the decreased conversion of nitrates to nitric oxide, possibly due to depletion of sulfhydryl cofactors. In vivo data do not completely support this sulfhydryl-depletion hypothesis. While supplementation with acetylcysteine does augment nitrate effects in vivo, the mechanism of intracellular sulfhydryl group repletion is inadequate in explaining the reversal of nitrate tolerance; an extracellular thiol/nitrate interaction appears to enhance vasodilation. Acetylcysteine inhibits angiotensin converting enzyme (ACE) in vivo and acts as an antioxidant, two mechanisms that may preserve the function of nitroglycerin-derived nitric oxide (NO). These potential actions indicate that acetylcysteine may protect the neurohormonal or vasoconstrictive responses to nitrates, rather than act as a simple repeller of thiol stores.


Acetylcysteine is administered orally, intravenously, or by inhalation. Once in the systemic circulation, 66% to 87% of the drug is bound to plasma proteins. Any acetylcysteine that is absorbed systemically is deacetylated by the liver and intracellularly in most tissues to cysteine and disulfides. Cysteine is then further metabolized to glutathione, as well as other metabolites. Most of an acetylcysteine dose is expected to be metabolized and incorporated as cysteine into cellular pools. The mean terminal half-life of the intravenous solution is 5.6 hours, while the effervescent tablets have a reported mean terminal half-life of 18.1 hours. Renal clearance accounts for roughly 30% of total clearance. After 24 hours, 13% to 38% of a radioactive dose of S-acetylcysteine is excreted in the urine. No metabolites have been identified in the urine. Only about 3% of acetylcysteine is excreted in feces.
Affected cytochrome P450 isoenzymes: none

Oral Route

Acetylcysteine is rapidly absorbed with peak plasma concentrations reached approximately 2 hours (range, 1 to 3.5 hours) after oral administration; however, oral bioavailability is very low (approximately 9%).

Intravenous Route

The Vdss and protein binding for the IV formulation of acetylcysteine are reported to be 0.47 L/kg and 83%, respectively.

Inhalation Route

After oral inhalation, the majority of the administered dose undergoes a sulfhydryl-disulfide reaction; only a small portion of the dose is absorbed from the pulmonary epithelium.

Other Route(s)

Intratracheal Route
After intratracheal instillation, the majority of the administered dose undergoes a sulfhydryl-disulfide reaction; only a small portion of the dose is absorbed from the pulmonary epithelium.

Pregnancy And Lactation

Adequate and well-controlled studies have not been performed in women receiving acetylcysteine during pregnancy; however, acetylcysteine does cross the placenta and has been detected in the cord blood of infants whose mothers received the drug at delivery. Four pregnant women with acetaminophen toxicity received oral or intravenous acetylcysteine at the time of delivery, and all of the women recovered. Three of the four neonates survived with no evidence of acetaminophen toxicity; one neonate (22 weeks gestational age) died shortly after delivery. Also, other limited case reports of pregnant women who received acetylcysteine during various trimesters have not reported adverse maternal, fetal, or neonatal outcomes. Of note, acetaminophen is also known to cross the placenta. Delaying treatment of pregnant women with acetaminophen overdose may increase the risk for maternal and fetal morbidity and mortality.

According to the manufacturer, it is not known whether acetylcysteine is distributed into human milk; use caution when acetylcysteine is administered to a nursing mother. Intravenous acetylcysteine is nearly completely eliminated within 30 hours after administration; therefore, mothers may consider reinitiating breast-feeding 30 hours after administration. Consider the benefits of breast-feeding, the risk of potential infant drug exposure, and the risk of an untreated or inadequately treated condition. If a breast-feeding infant experiences an adverse effect related to a maternally administered drug, healthcare providers are encouraged to report the adverse effect to the FDA.