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An Essential Medication for Respiratory Health

Last Modified: 21 May 2024

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What is Acetylcysteine?

Acetylcysteine, also known as N-acetylcysteine (NAC), is a medication derived from the amino acid L-cysteine. It is a potent antioxidant and mucolytic agent that helps thin and loosen mucus in the airways. 

Quick Breakdown of Acetylcysteine's Structure 

Acetylcysteine is made by introducing an acetyl group into the amino acid cysteine. The chemical structure of Acetylcysteine allows it to break disulfide bonds in mucus, making it less viscous. 

Global Name

Acetylcysteine, also known as N-acetylcysteine (NAC), is known by various brand names globally as listed below.  

Generic Name and Brand Names 

  • Generic name: Acetylcysteine or N-acetylcysteine 
  • Brand names: Mucomyst, Acetadote, Parvolex, and Fluimucil, among others. 


What is Acetylcysteine used for?

With its mucolytic and antioxidant properties, acetylcysteine serves multiple therapeutic roles in respiratory and non-respiratory conditions. 

Respiratory Conditions 

  • Chronic Obstructive Pulmonary Disease (COPD): Helps relieve mucus build-up. 
  • Cystic Fibrosis: Eases mucus clearance, reducing the frequency of chest infections. 
  • Bronchitis: Alleviates mucus obstruction in the bronchial tubes. 
  • Pneumonia: Assists in the management of pulmonary secretions and promotes recovery. 
  • Asthma: Used cautiously to aid in thinning mucus, especially during an exacerbation. 

Acetaminophen Overdose 

Acetylcysteine is a lifesaving antidote for overdoses of acetaminophen (aka paracetamol) (Tylenol®, Panadol®, Alvedon®). It protects the liver by restoring glutathione levels, a vital antioxidant necessary to detoxify harmful substances in the liver. 

Other Potential Medical Uses (Investigational) 

  • Psychiatric Disorders: Emerging evidence suggests potential benefits in conditions like depression and bipolar disorder due to its impact on neurotransmitters and neuroprotection. 
  • Neurological Protection: There is ongoing research into its role in preventing neurodegeneration in diseases like Alzheimer's and Parkinson's. 

How do you use Acetylcysteine?


  • Inhalational solution 
  • Solution for intravenous use 
  • Oral forms: solution, tablet, capsule and powder 
  • Ocular (eye) solution 

Dosage Information 

  • Adults: 600 mg orally once daily. 
  • Children: Dose varies based on age and weight; consult a paediatrician. 

Suitability Across Different Ages and Conditions 

  • Children: Suitable with adjusted dosage. 
  • Adults: Standard dosage applies. 
  • Elderlies: May require dosage adjustment based on renal function and concomitant use of other medications. 
  • Pregnancy and Lactation (breastfeeding/nursing mothers) 
    • Pregnancy – weigh risk vs. Benefits, US FDA cat. B (No risk in animal studies (there are no adequate studies in humans, but animal studies did not demonstrate a risk to the fetus)  
    • Nursing/breastfeeding - advised to wait 30 hrs. After intake before resuming breastfeeding 

Warnings and Precautions 

  • Take with food if a gastrointestinal upset occurs. 
  • Monitor for allergic reactions. 

Interactions and Contraindications 

  • Drug Interactions: These may interact with activated charcoal and nitroglycerin. 
  • Food Interactions: No significant food interactions. 
  • Contraindications 
    • Hypersensitivity to the drug, peptic ulcer. 
    • Allergic Reactions: Not suitable for those allergic to Acetylcysteine. 
    • Pregnancy and Breastfeeding: Consult a doctor before use. 
    • Asthma: Use with caution; may cause bronchospasm. 

Side Effects

Common side effects include nausea, vomiting, and diarrhoea. Rarely, it can cause anaphylaxis or severe skin reactions. 

Pharmacist Tips

Storage Information 

  • Store at room temperature, away from direct sunlight. 

Handling Instructions 

  • Mix the oral solution with water, juice, or soda to improve the taste. 


  • Try to take your doses simultaneously each day for consistent therapeutic levels in your body. 


Where is Acetylcysteine available in Hong Kong?

It is usually provided under medical prescription for its various uses, such as a mucolytic agent in respiratory conditions and for acetaminophen (paracetamol) overdose.

For over-the-counter use, particularly as a dietary supplement, the availability could vary, and regulation might differ from its use as a prescription medication. 


Carbocysteine vs Acetylcysteine, which is better? 

Carbocysteine and acetylcysteine are mucolytic agents that help liquefy thick mucus, making it easier to expel from the respiratory tract. While both can effectively manage conditions like chronic bronchitis or COPD, their additional properties differ. Acetylcysteine has a unique role as an antidote for acetaminophen (paracetamol) overdose. The choice between the two often depends on the individual patient's needs, potential side effects, and the specific clinical situation  

Bromhexine vs Acetylcysteine, which is better? 

Bromhexine and acetylcysteine are used to break down mucus, aiding in the clearance of secretions from the respiratory tract. Bromhexine breaks down mucus's structure directly, while acetylcysteine reduces mucus viscosity has antioxidant properties, and is an antidote for acetaminophen overdose. Their choice depends on individual patient factors, including efficacy, tolerance, side effects, and specific clinical scenarios. There is no one-size-fits-all answer; the "better" option is determined by a healthcare provider based on the patient's unique medical history, condition, and response to treatment. 

Can Acetylcysteine be used for coughs associated with colds? 

Yes, it can be used to reduce mucus in the airways caused by colds. 

How quickly does Acetylcysteine work? 

It begins to take effect within 1 hour of ingestion, with peak effects at 2-3 hours. 

Can Acetylcysteine be taken with other over-the-counter medications? 

Consult a healthcare provider as it may interact with other drugs. 

This website provides content related to drug use and medicine for informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Do not use the information on this website to diagnose or treat a health problem or disease without consulting a qualified healthcare provider. The website's owners and contributors are not liable for any repercussions, adverse effects, or consequences resulting from the use of any medication or information provided herein.

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