> Western Medicines > Dextromethorphan


Used for: Dry cough
Chinese name:

What is Dextromethorphan for?

Dextromethorphan belongs to a group of medications called antitussives. It is a cough suppressant used to provide symptomatic relief of dry coughs caused by the common cold (no phlegm) and bronchial irritation. It reduces your feeling of need to cough by decreasing activity in certain parts of the brain that cause coughing.

How to use it?

Dextromethorphan is commonly abbreviated as DM on cough and cold products. It is available in single-ingredient products but is also available in many combination cough and cold products. Dextromethorphan is taken by mouth and can be used in adults and children older than 4 years old. For the conventional preparation, you should take 12-40 mg every 4 hours or 30 mg every 6-8 hours and the maximum dose is 120 mg daily. For the extended-release preparation, you should take 60 mg every 12 hours and the maximum dose is 120 mg daily. For lozenges, you should suck no more than 12 lozenges daily.

What are the side effects of Dextromethorphan?

Common side effects of Dextromethorphan include dizziness, drowsiness, and fatigue. Avoid driving or operating machinery until you know how you respond to Dextromethorphan.

Who should not take Dextromethorphan?

People who are taking an monoamine oxidase (MAO) inhibitor to treat depression and if they have stopped taking an MAO inhibitor within the past 2 weeks.

Pharmacist Tips:

Dextromethorphan can cause serotonin syndrome if taken together with selective serotonin reuptake inhibitors (SSRI), serotonin-norepinephrine reuptake inhibitors (SNRI) or triptans. Symptoms include agitation, increased heartbeat, quick involuntary muscle twitching, sweating, etc. Stop taking the medicine and seek immediate medical attention.


Common dosing schedule: 
You can take Dextromethorphan with or without food.


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


Some common medications Dextromethorphan may interact with:

Please notify your doctor or pharmacist if you are taking the above medication, dosage adjustments might be needed.

Where to buy Dextromethorphan in Hong Kong?

In Hong Kong, the classification of Dextromethorphan depends on its concentration in the preparation. It can be 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. Some are pharmacy-only products. Dextromethorphan 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 Dextromethorphan 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
Robitussin DM
Tussidex Forte
Available dosage
  • 7.5mg/5ml / 15mg/5ml (Syrup)
  • 15mg / 25mg / 30mg (Tablets)
Drug class
Cough and Common Cold Medicines
Sub class
Cough Suppressants (Antitussives)
Other drugs in same class