How does promethazine work?
Promethazine blocks histamine receptors, reducing allergy symptoms. It also affects areas of the brain that control nausea and vomiting, and has a calming effect that can help with sleep.
What is promethazine used to treat?
Promethazine is commonly prescribed for:
- Allergies (hay fever, skin reactions, and insect bites)
- Motion sickness and travel sickness
- Nausea and vomiting
- Short-term sleep problems (insomnia)
- Coughs and colds (as part of combination medicines)
Who can take promethazine?
Promethazine is suitable for most adults and children over 2 years old, but some forms should only be used in older children.
Who might not be able to take promethazine?
Promethazine may not be suitable if you:
- Have severe breathing problems (such as COPD or sleep apnoea)
- Have glaucoma
- Have epilepsy
- Are taking certain antidepressants or sedatives
Can I take promethazine if I’m pregnant or breastfeeding?
Promethazine isn’t usually recommended during pregnancy or while breastfeeding unless advised by a doctor.
What if I miss a dose?
If you forget a dose, take it as soon as you remember. If it’s close to your next dose, skip the missed one—do not take two doses at once.
How effective is promethazine?
Promethazine is effective for allergies, nausea, and sleep issues, typically working within 30 minutes to 1 hour.
What should I do if I take too much?
Taking too much promethazine can cause severe drowsiness, confusion, dizziness, or difficulty breathing. If you think you’ve taken too much, seek emergency medical help immediately.
What dose of promethazine is usually taken?
- For allergies: 10mg to 20mg once or twice daily
- For motion sickness: 25mg before travel, then every 6 to 8 hours if needed
- For nausea and vomiting: 25mg when needed
- For sleep problems: 25mg to 50mg before bedtime
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What are the side effects of promethazine?
Common side effects include:
Serious side effects, such as breathing difficulties or severe allergic reactions, require urgent medical attention.
How should I take promethazine?
Promethazine is taken as tablets, liquid, or suppositories, depending on the condition being treated.
When should promethazine be taken?
Promethazine can be taken with or without food, usually before bedtime if being used as a sleep aid.
What are the brand names for promethazine?
Promethazine is available as a generic medicine, but some branded versions include:
- Phenergan
- Sominex (for sleep problems)
Final thoughts
Promethazine is an effective antihistamine for allergies, nausea, and sleep problems, but it can cause drowsiness. To get the best results, take it as prescribed and avoid alcohol. If you experience side effects, speak to your doctor or pharmacist.
