Pharmacology
DrugBankDescription
Acetylcysteine is an antioxidant and glutathione inducer indicated for mucolytic therapy and the treatment of acetaminophen overdose. Acetylcysteine has also been studied for a wide variety of off-label indications with mixed results. Acetylcysteine was granted FDA approval on 14 September 1963.
Mechanism of Action
A number of possible mechanisms for the mucolytic activity of acetylcysteine have been proposed. Acetylcysteine's sulfhydryl groups may hydrolize disulfide bonds within mucin, breaking down the oligomers, and making the mucin less viscous. Acetylcysteine has also been shown to reduce mucin secretion in rat models. It is an antioxidant in its own right but is also deacetylated to cysteine, which participates in the synthesis of the antioxidant glutathione. The antioxidant activity may also alter intracellular redox reactions, decreasing phosphorylation of EGFR and MAPK, which decrease transcription of the gene MUC5AC which produces mucin. In the case of acetaminophen overdoses, a portion of the drug is metabolized by CYP2E1 to form the potentially toxic metabolite N-acetyl-p-benzoquinone imine (NAPQI). The amount of NAPQI produced in an overdose saturates and depletes glutathione stores. The free NAPQI promiscuously binds to proteins in hepatocytes, leading to cellular necrosis. Acetylcysteine can directly conjugate NAPQI or provide cysteine for glutathione production and NAPQI conjugation.
Pharmacodynamics
Acetylcysteine is indicated for mucolytic therapy and in the management of acetaminophen overdose. It has a short duration of action as it is given every 1-8 hours depending on route of administration, and has a wide therapeutic window. Patients should be counselled regarding diluting oral solutions in cola for taste masking, the risk of hypersensitivity, and the risk of upper gastrointestinal hemorrhage.
Metabolism
Acetylcysteine can be deacetylated by aminoacylase 1 or other undefined deacetylases before undergoing the normal metabolism of cysteine.
Absorption
An 11 g dose in the form of an effervescent tablet for solution reaches a mean Cmax of 26.5 µg/mL, with a Tmax of 2 hours, and an AUC of 186 µg\*h/mL.
Toxicity
Patients experiencing an overdose may present with vomiting, nausea, bronchospasm, periorbital angioedema, and hypotension. Treat patients with symptomatic and supportive measures. Hemodialysis may remove some acetylcysteine from circulation as it is somewhat protein bound.
Indication
Acetylcysteine is indicated for mucolytic therapy and in the management of acetaminophen overdose.
Half-life
The mean terminal half life of acetylcysteine in adults is 5.6 hours and in pre-term neonates is 11 hours.
Protein Binding
Acetylcysteine is 66-97% protein bound in serum, usually to albumin.
Elimination
An oral dose of radiolabelled acetylcysteine is 13-38% recovered in the urine in the first 24 hours, while 3% is recovered in the feces.
Volume of Distribution
The volume of distribution of acetylcysteine is 0.47 L/kg.
Clearance
Acetylcysteine has a mean clearance of 0.11 L/hr/kg.
Receptor Profile
Receptor Actions
Receptor Binding
Tolerance & Pharmacokinetics
drugs.wikiTolerance Decay
References
Data Sources
Cited References
- Examine.com: N-Acetylcysteine
- Lee et al. 2014: NAC modulates hallucinogenic 5-HT2A receptor agonist responses
- NCBI StatPearls: N-Acetylcysteine
- Nootropics Expert: NAC Guide
- PMC: Gray et al. 2010 - NAC in Young Marijuana Users
- PMC: Multifaceted Therapeutic Role of NAC
- PMC: NAC as potential treatment for substance use disorders
- PMC: NAC Impacts on Human Health