Promethazine is an antihistamine.
You may need to take one or more doses during a day, depending upon the reason you are taking it. Make sure you carefully follow the directions on the label.
Promethazine may affect your ability to drive and to use tools or machines.
The most common side-effects are feeling sleepy, headache, dry mouth and blurred vision.
|Type of medicine||An antihistamine|
|Used for||Allergic conditions such as hay fever; to prevent sickness (nausea); and as a sedative|
|Also called||Avomine®, Vertigon® (promethazine teoclate); Phenergan®, Sominex® (promethazine hydrochloride)|
|Available as||Tablets, oral liquid and injection|
Promethazine belongs to a group of medicines known as sedating antihistamines. It has several uses.
Promethazine also makes you feel sleepy (has a sedative effect). It may be taken (for a few days only) to help promote sleep in adults with sleeping problems. It has been popular in the past as a means of 'settling' children, but promethazine should not be used in this way.
Promethazine is available on prescription, or you can buy it without a prescription at pharmacies. It is not suitable for children under 2 years of age.
Before taking promethazine
To make sure this is the right treatment for you, before you start taking promethazine it is important that you discuss the treatment with a doctor or pharmacist if:
- You are pregnant, trying for a baby or breastfeeding.
- You have a problem with the way your liver works, or if you have a problem with your kidneys.
- You have a condition which causes increased pressure in your eyes, such as glaucoma.
- You have prostate problems or if you have been experiencing any difficulty passing urine.
- You know you have a blockage in your small intestines.
- You have epilepsy.
- You have any long-term breathing problems, such as asthma or chronic obstructive pulmonary disease (COPD).
- You are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, as well as herbal and complementary medicines.
- You have ever had an allergic reaction to a medicine.
How to take promethazine
- Before you start this treatment, read the manufacturer's printed information leaflet from inside your pack. There are a number of different brands and strengths of promethazine tablet. The manufacturer's leaflet will give you more information about the brand you have been given. It will also contain a full list of the side-effects which you may experience from taking promethazine.
- Take promethazine exactly as your doctor or pharmacist has told you to. You may be asked to take one or more doses during a day, depending upon the reason why you are taking it.
- If you are taking promethazine to prevent travel sickness, it is usually recommended that you take the first dose at bedtime on the evening before you are due to travel. You can then take a further dose on the morning of your travel if needed.
- You can take promethazine before or after meals. Some people find it helps to swallow the tablets with a drink of water.
- If you are giving promethazine liquid medicine to a child, make sure you follow the dosing instructions on the bottle carefully so that you measure out the correct dose for the age of your child.
- Most people only need to take an antihistamine for a short while when they have symptoms. You should stop taking promethazine once your symptoms have eased. Do not take promethazine for more than a few days for sleeping problems.
Getting the most from your treatment
- Promethazine may cause drowsiness and blurred vision. If this happens to you, do not drive and do not use tools or machines. Alcohol will make the drowsiness worse, so it is best not to drink alcohol while you are on promethazine.
- If you are pregnant, only take promethazine on the advice of your doctor. Do not take promethazine in the last two weeks before your baby is born as it could cause side-effects for your baby.
- If you are having an operation or any treatment (particularly if it is to test for an allergy), tell the person carrying out the treatment that you are taking promethazine.
- Promethazine may cause your skin to become more sensitive to sunlight than normal. Use a sunscreen that protects against UVA light and has a sun protection factor (SPF) of at least 15, especially in strong sunlight or until you know how your skin reacts. Do not use sunbeds.
- If you buy any medicines, check with a pharmacist that they are safe to take with an antihistamine. This is because a number of other medicines can interfere with the way promethazine works and can increase the risk of side-effects.
Can promethazine cause problems?
Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains the most common ones associated with promethazine. You will find a full list in the manufacturer's information leaflet supplied with your medicine. The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any continue or become troublesome.
|Common promethazine side-effects||What can I do if I experience this?|
|Feeling dizzy or sleepy, and blurred vision||Do not drive and do not use tools or machines. Do not drink alcohol|
|Headache||Drink plenty of water and ask your pharmacist to recommend a suitable painkiller. If the headaches continue, stop taking promethazine or speak with your doctor|
|Dry mouth||Try sucking sugar-free sweets or chewing sugar-free gum|
|Difficulty passing urine||Speak with your doctor if this becomes troublesome|
|Stomach upset, constipation||Try to eat a well-balanced diet and drink plenty of water|
If you experience any other symptoms which you think may be due to this medicine, speak with your doctor or pharmacist.
How to store promethazine
- Keep all medicines out of the reach and sight of children.
- Store in a cool, dry place, away from direct heat and light.
Important information about all medicines
Never take more than the prescribed dose. If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.
This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.
Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.
If you have any questions about this medicine ask your pharmacist.
Further reading and references
Manufacturer's PIL, Phenergan® 10 mg Tablets; Sanofi, The electronic Medicines Compendium. Dated August 2019.
Manufacturer's PIL, Sominex® 20 mg Tablets; Teva UK Ltd, The electronic Medicines Compendium. Dated February 2018.
British National Formulary, 79th Edition (Mar 2020); British Medical Association and Royal Pharmaceutical Society of Great Britain, London.