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Promethazine

Chinese name:

異丙嗪

Reviewed by

Joseph Blais, Pharmacist

Expert Advisory Board Member

Last Updated: 2022-04-29

What is Promethazine for?

Promethazine is a sedating (first generation) antihistamine. It has a wide range of uses including treating allergic conditions, inducing sedation, short-term management of insomnia, treating nausea and vomiting, and preventing and treating motion sickness. Antihistamines can also be used to manage the symptoms of the common cold such as runny nose and sneezing. Promethazine relieves symptoms of itching, runny nose, watery eyes and sneezing.

In Hong Kong, it is frequently found in combination products used for treating coughs and colds.

How to use it?

The oral doses for different age groups and uses are listed below:

For allergic conditions

Adult
As Promethazine HCl: 25 mg at night, increase if necessary to 25 mg twice daily OR 10-20 mg 2-3 times daily.

Child 2-5 years
As Promethazine HCl: 5-15 mg daily in 1-2 divided doses.

Child 5-10 years
As Promethazine HCl: 10-25 mg daily in 1-2 divided doses.

For short-term management of insomnia

Adult
As Promethazine HCl: 20-50 mg at night.

For nausea and vomiting

Adult
As Promethazine teoclate: 25 mg at night, may increase the dose to 50-75 mg at night or to 25 mg 2-3 times daily if necessary up to a maximum of 100 mg daily.

For prevention of motion sickness

Adult
As Promethazine HCl: 20 or 25 mg the night before travelling and repeat in the next morning if necessary.

As Promethazine teoclate: 25 mg at night or 1-2 hour before travelling.

Child 2-5 years
As Promethazine HCl: 5 mg the night before the journey and repeat in the next morning (after 6-8 hours) if necessary.

Child 5-10 years
As Promethazine HCl: 10 mg the night before the journey and repeat in the next morning (after 6-8 hours) if necessary.

As Promethazine teoclate: 12.5 mg the night or 1-2 hour before travelling.

What are the side effects of Promethazine?

Common side effects of Promethazine include dizziness and drowsiness, constipation, blurred vision, and dry mouth.

Who should not take Promethazine?

People with an allergy to Promethazine or other ingredients of the formulation
Children under the age of 2

Pharmacist Tips:

Avoid taking Promethazine if you are 65 years and older as you are at higher risk of side effects, such as confusion, dry mouth and constipation.
As Promethazine can cause drowsiness, do not drive or operate machinery if affected.

Common dosing schedule:
You can take Promethazine with food to reduce gastrointestinal upset.

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

Some common medications Promethazine may interact with:

Alcohol
Clozapine
Flunitrazepam
Ipratropium
Other antihistamine, e.g. Chlorpheniramine, Fexofenadine, Levocetirizine, Loratadine

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

Where to buy Promethazine in Hong Kong?

In Hong Kong, Promethazine 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 Promethazine 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.

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