If you or your child have been prescribed promethazine, follow your doctor's instructions about how and when to take it.
Only take promethazine when you need it. For example, take it if you're unable to sleep because you're worrying about something or if your cold symptoms are keeping you awake.
If you've bought promethazine or any medicine containing promethazine from a pharmacy, follow the instructions that come with it, or ask a pharmacist for advice.
Dosage and how to take promethazine
Dosage and strength
Promethazine tablets come in strengths of 10mg, 20mg or 25mg.
The liquid contains 5mg of promethazine in 5ml.
If you're taking liquid promethazine, follow the instructions that come with the medicine for how much to take.
For adults and children aged 10 years or older, your dose depends on why you're taking it.
For hay fever or hives the dose can vary from 10mg twice a day to 20mg 3 times a day or 25mg once or twice a day.
For preventing motion sickness you'll usually take 25mg the night before your journey. Some products only need to be taken 1 to 2 hours before travelling, if it's a short journey.
For treating motion sickness take 25mg as soon as possible and 25mg the same evening. You can then take 25mg the following evening, if you need it.
For vertigo the dose can vary from 25mg a day to 25mg 4 times a day.
For short-term sleep problems you'll usually take 20mg to 50mg at night.
Doses are lower for children aged 9 years or under. To find out what dose to give your child, ask your doctor or pharmacist for advice or check the medicine packet.
Dosage for promethazine mixed with other medicines
Promethazine can come mixed with other medicines, such as paracetamol. This is usually used to treat cough and cold symptoms. Your dose will depend on the type of medicine you're taking.
Check the instructions on the packaging for how much to take. Ask your pharmacist or doctor if you're unsure.
How to take it
You can take promethazine with or without food.
How to take tablets
Always take your promethazine tablets with a drink of water. Swallow them whole. Do not chew them.
How to take liquid
Liquid medicines containing promethazine come with a plastic syringe or spoon to help you measure out the right dose.
If you do not have a syringe or spoon, ask your pharmacist for one. Do not use a kitchen teaspoon as it will not measure the right amount.
How long to take it for
Only take promethazine for a short time, unless your doctor says it's OK for you to take it for longer.
Speak to your pharmacist or doctor before taking promethazine for longer than the medicine leaflet recommends.
Ask them for advice if you're unsure how long you should take it for.
If you forget to take it
If you're taking promethazine for motion sickness and you forget a dose, take it as soon as you remember.
If you're taking it for anything else, skip the missed dose and take your next dose at the usual time.
Never take 2 doses at the same time. Never take an extra dose to make up for a forgotten one.
If you often forget doses, it may help to set an alarm to remind you. You could also ask your pharmacist for advice on other ways to help you remember to take your medicine.
If you take too much
Taking too much promethazine can be dangerous. It's important to get medical advice if you take more than the recommended dose.
Immediate action required: Call 999 or go to A&E now if:
You or your child take more than the recommended dose of promethazine and:
- have a very fast, irregular or pounding heartbeat
- have breathing problems
- have a seizure or fit
- become unconscious
- have uncontrolled movements, especially in the hands or feet
- see or hear things that are not there (hallucinations)
- your child moves unsteadily or stumbles
Urgent advice: Contact 111 for advice if:
- you or your child takes more than the recommended dose of promethazine, even if you do not have any symptoms
Call 111 or get help from 111 online. Call 111 if you're asking about a child under 5 years old.
If you need to go to A&E, do not drive. Ask someone to drive you or call 999 and ask for an ambulance.
Bring the promethazine packet or leaflet inside it, any remaining medicine, and any other medicines you take.
Stopping promethazine
If you've taken promethazine for a long time and suddenly stop taking it, it's possible you might feel dizzy, sweaty or sick, have a racing heart and have trouble sleeping.
Coming off promethazine slowly can help prevent this.
Speak to your doctor if you've taken promethazine for a long time and want to stop taking it.