Promethazine is used for relief of itch, redness and swelling of the eyes, nose or skin (due to an insect bite or allergies). Learn how to use the medication, its common side effects, special precautions to watch out for, and more.

What is this medication for?

Promethazine belongs to a group of medicines known as antihistamines. Antihistamines are a group of medications which can be used for the following conditions:

• Relief of redness and swelling of the skin and eyes 
• Relief of itch in the eyes, nose or skin (due to an insect bite or allergies)

It can also be used to:

• Treat nausea or vomiting 
• Prevent or treat motion sickness
• Help you to fall asleep 

Promethazine may be used for other conditions. Check with your healthcare professional if you are unsure why you are given this medication.

How should I take or use this medication?

• Promethazine may be taken with or without food.
• Take your medication according to the instructions stated on the medication label.
• Do not stop taking or adjust the dose of this medication without checking with your doctor.
• Do check with your doctor on how long you will have to be on this medication.

What should I do if I forget to take or use this medication?

• If you have been told by your doctor to take Promethazine regularly but you forget to take a dose, take it as soon as you remember. However, if more than half of the time to the next dose has passed, skip the missed dose and take the next dose at your usual timing.
• For example, for a medication to be taken two times daily at 8am and 8pm, and you missed your first dose at 8am, skip the first dose if it is after 2pm, and take your second dose at the usual timing at 8pm. Do not take two doses to make up for the missed dose.

What precautions should I take when taking or using this medication?

Inform your healthcare professional if: 

• You are allergic to this medication or any of the other ingredients of this medication
• You are pregnant, planning to become pregnant, or breastfeeding. If you are pregnant and/or breastfeeding, your doctor would have discussed the potential benefits and side-effects with you and should you have further questions or concerns, do consult your doctor.
• You are taking any other medications (including those that can be bought without a prescription), supplements, traditional medications and herbal remedies. Some of them may affect how this medication works or cause serious drug interactions.
• You have or have ever had:
  • Other drug allergies
  • Kidney or liver disease
  • High blood pressure or abnormal heart rhythm
  • Respiratory disease
  • Medical conditions such as difficulty in urination, enlarged prostate gland, stomach ulcers, overactive thyroid gland (hyperthyroidism), seizures (fits) or increased eye pressure (glaucoma)

What are some common side effects of this medication?

• Drowsiness or feeling tired
  • Avoid driving or taking part in activities that require concentration
  • Discuss with your doctor if you can take your medication at a different time of the day
• Dizziness
  • Get up slowly from a sitting or lying down position
• Dry mouth
  • Chew sugar-free gum, suck on sugar-free hard candies or ice chips, or take sips of water regularly
• Constipation 
  • Drink more water (if you do not have any fluid restriction), eat more high-fibre foods, and exercise regularly
  • Speak to your doctor or pharmacist if you need medication to help with your constipation
• Headache

Most of the side effects listed here will improve with time. Speak with your doctor if any of them continues, worsens or affects your daily life.

What are some rare but serious side-effects that I need to seek medical advice immediately?

The symptoms of a drug allergy include one or more of the following: 

• Swollen face/eyes/lips/tongue
• Difficulty in breathing
• Itchy skin rashes over your whole body

Rarely, this medication may cause:

• Restless muscle movements in your eyes, tongue, jaw or neck (dyskinesia)
• Confusion, high fever, severe muscle stiffness, irregular blood pressure (signs and symptoms of neuroleptic malignant syndrome)
• Seeing or hearing things that are not there (hallucinations)
• Confusion
• Fast or irregular heartbeat, fainting episodes (signs and symptoms of an abnormal heart beating rhythm (prolonged QTc interval))
• Tremors
• Seizures (fits)
• Blurred vision

If you experience any of these symptoms, you should stop your medication and see your healthcare professional immediately.

What food or medication should I avoid when I take or use this medication?

Avoid drinking alcohol while taking Promethazine as it can cause excessive sleepiness.

How should I store this medication?

Store in a cool and dry place, away from direct sunlight. Keep this medication away from children. 

How do I throw away this medication safely?

Pack this medication into a trash bag and seal it tightly before throwing into the rubbish chute or bin. 

Disclaimer

Please take note that the above is not a complete list of all possible side effects. If you have any concerns about your medication or if you have other side effects that you think are caused by this medication, please consult your doctor or pharmacist.

If you take more than the recommended dose, please seek medical advice immediately. The information provided on this page does not replace information from your healthcare professional. Please consult your healthcare professional for more information.

This article is jointly developed by members of the National Medication Information workgroup. The workgroup consists of cluster partners (National Healthcare Group, National University Health System and SingHealth), community pharmacies (Guardian, Unity and Watsons) and Pharmaceutical Society of Singapore. The content does not reflect drug availability and supply information in pharmacies and healthcare institutions. You are advised to check with the respective institutions for such information.

Last updated on Feb 2025