> Western Medicines > Acetylcysteine


Chinese name:

What is Acetylcysteine for?

Acetylcysteine belongs to a class of medications called mucolytic agents. It works by breaking down the disulfide bonds to give thinner mucus that can be coughed out more easily. Therefore, it is most commonly used for treating wet cough. In addition, Acetylcysteine is the antidote for Paracetamol/Acetaminophen overdose.

How to use it?

Acetylcysteine can be taken by mouth, inhaled, or given by injection.


If you are taking Acetylcysteine for wet cough, the usual adult dose is to take 600 mg per day. This can be taken once per day or divided into 200 mg three times a day. When used for inhalation, the dose will vary based on the concentration of the product used. Acetylcysteine is nebulized and inhaled 3 to 4 times per day.

What are the side effects of Acetylcysteine?

Side effects of oral Acetylcysteine are uncommon and mostly occur in adults, including diarrhoea, nausea and vomiting. A rare but concerning side effect of Acetylcysteine by injection is anaphylaxis (e.g., itching, flushing, hives, difficulty breathing). Inhaled Acetylcysteine causes bronchospasm so you will normally receive a dose of a bronchodilator (e.g. Salbutamol) before each inhaled dose of Acetylcysteine.

Who should not take Acetylcysteine?

  • People who are hypersensitive to acetylcysteine or other components of the drug.

Pharmacist Tips:

Drink more water to help this medication to exert its effect. Some products may have a sulfur or “rotten egg” odour or taste. If palatability is a concern, a powder form for diluting into cold water, producing an orange-flavoured solution is available in Hong Kong (Hence the Chinese nickname Orange Tree). Or you can mix it in with other food to mask the smell and taste.


Common dosing schedule:
Acetylcysteine can be taken with or without food.


This schedule is for reference only, adjustments may be made according to individual needs.


Some common medications Acetylcysteine may interact with:

  • N/A

Where to buy Acetylcysteine in Hong Kong?

In Hong Kong, Acetylcysteine is an over-the-counter medicine which can be purchased without a prescription from any retail outlet in Hong Kong. This includes grocery stores, convenience stores, medicine shops, and pharmacies. It can also be obtained from doctors. To find a pharmacy near you, refer to the list of pharmacies (“Authorized Sellers of Poisons”) from the Hong Kong Department of Health.


For more information about drug names and ingredients, you can visit Hong Kong’s Drug Office at https://www.drugoffice.gov.hk

Need more information?

For detailed information about the use of Acetylcysteine in children, pregnancy and breastfeeding, and for questions about drug interactions, please check with your pharmacist or doctor.

Disclaimer: our goal is to provide you with the most relevant drug information and common dosage for Hong Kong. This information does not constitute medical advice. For specific treatment recommendations and advice, always discuss with your doctor or pharmacist, and follow the instructions included with your specific medicine.

Brands in Hong Kong
Available dosage
  • 600mg (Effervescent Tablets)
  • 100mg / 200mg (Granules)
  • 300mg/3ml (Injections)
Drug class
Cough and Common Cold Medicines
Sub class
Other drugs in same class