How do you take Promethazine?

For allergies, take one 25 mg tablet at night before bed or 25 mg twice daily. For nausea or travel sickness, take 25 mg about 30 minutes to 1 hour before travelling. You can take it with or without food, but taking it with food can help reduce stomach upset. This drug makes you very sleepy, so avoid taking it when you need to be alert.

What are the side effects of Promethazine?

Feeling very sleepy or drowsy, dry mouth, dizziness, blurred vision, constipation

Who should not take Promethazine?

Children under 2 years old, people with severe liver disease, people with breathing problems like asthma (it can worsen it), people who are allergic to promethazine or similar drugs, people who have had seizures (convulsions), and people currently taking MAO inhibitor drugs.

OTC

Antihistamine (sedating)

Promethazine

Q: What is Promethazine used for?

Allergies (sneezing, itching, watery eyes, skin rash), nausea and vomiting, motion sickness (travel sickness), trouble sleeping, cough and cold symptoms

Last reviewed July 2026

Who is this for?

For adults (18+). Standard adult dosing applies: see the How to Take tab for full instructions.

What is this drug?

Promethazine is an antihistamine drug that works by blocking a chemical called histamine in your body, which helps stop allergic reactions, nausea, vomiting, and also makes you feel sleepy.

How it works

Blocks H1 histamine receptors in the central and peripheral nervous system, suppressing allergic responses and pruritus, while antagonising muscarinic cholinergic receptors to provide antiemetic and anticough effects. The central H1 blockade also produces sedation through depression of the reticular activating system.

What is it used for?

Allergies (sneezingitchingwatery eyesskin rash)nausea and vomitingmotion sickness (travel sickness)trouble sleepingcough and cold symptoms

Browse by condition

Cough & Cold Allergies Nausea & Vomiting Eczema & Skin Rashes Anxiety & Sleep Problems

Available Over The Counter

Get this from any pharmacy or chemist: no prescription needed.

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What to watch out for

This drug causes serious drowsiness, so do not drive, ride okada, or operate machines after taking it. Do not combine it with tramadol or codeine bought from roadside sellers, as this combination is very dangerous and has caused deaths in Nigeria. Always buy from a registered pharmacy and check the expiry date before use.

Common Side Effects

Feeling very sleepy or drowsy
dry mouth
dizziness
blurred vision
constipation

Serious Side Effects

Difficulty breathing or swallowing
which could be a severe allergic reaction: go to the hospital immediately. Uncontrollable movements of your face
tongue
or body (muscle stiffness or twitching). Severe yellowing of the eyes or skin
which indicates a liver problem: see a doctor immediately.

Drug Interactions

Alcohol: do not drink alcohol while taking promethazine as it will make the drowsiness much worse and can be dangerous. Tramadol and codeine: combining with promethazine increases the risk of extreme drowsiness and breathing problems. Sleeping pills or other sedatives: taking them together can make you dangerously sleepy.

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Pregnancy & Breastfeeding Warning

Promethazine is not considered safe during pregnancy, especially in the first trimester, and can pass into breast milk. Consult your doctor before using it if you are pregnant or breastfeeding.

Who Should NOT Take This

Children under 2 years old
people with severe liver disease
people with breathing problems like asthma (it can worsen it)
people who are allergic to promethazine or similar drugs
people who have had seizures (convulsions)
and people currently taking MAO inhibitor drugs.

How to Store

Store in a cool, dry place away from direct sunlight and heat. Nigerian weather can be very hot, so don't leave it in your car or near a window. Keep the container tightly closed and always store away from children.

For information only: not medical advice. Always talk to a doctor or pharmacist before changing your medication.