If you are wondering how many Phenergan (promethazine hydrochloride) tablets you can take, the answer depends on why you are taking the medicine.
For adults, the usual Phenergan 25mg tablet dose for short term insomnia is 25mg or 50mg as a single dose at night. For allergies such as hay fever or hives, the usual adult dose is 25mg at night, which may be increased to 25mg twice a day if needed. For motion sickness, the usual dose is 25mg, often taken the night before a journey and repeated after 6 to 8 hours if required.
There is no general 100mg daily maximum for Phenergan tablets that should be used as a target or routine dose. The correct maximum depends on why you are taking promethazine and the specific instructions for your medicine. Taking more than the recommended dose can be dangerous.
Phenergan contains promethazine, a sedating antihistamine. It can be used for allergy symptoms, motion sickness and, for short term use, insomnia in adults. It can make you sleepy or less alert, and its effects can last for several hours. The UK product information states that the duration of action can be up to 12 hours.
This guide explains the usual adult doses, when 1 or 2 tablets may be used, what to do if you take too much, and when to speak to a pharmacist or prescriber.
Key things to know
- For short term insomnia in adults, the usual dose is 1 or 2 Phenergan 25mg tablets at night
- For allergies, adults usually start with 1 tablet (25mg) at night, which may be increased to 1 tablet twice a day if needed
- For motion sickness, the usual adult dose is 1 tablet (25mg), with another dose after 6 to 8 hours if required
- There is no general 100mg maximum for Phenergan tablets that applies to every use
- Do not take more than the dose recommended for your condition
- Promethazine can cause drowsiness, dizziness and blurred vision, so do not drive or operate machinery if you are affected
- Do not drink alcohol while taking Phenergan because it can increase the sedating effect
How Many 25mg Tablets Is a Standard Dose for Hay Fever?
For adults, the Phenergan 25mg tablet information gives the following doses:
| Use | Typical tablet count |
|---|---|
| Allergy, such as hay fever, hives or rashes | 1 tablet (25mg) at night, which may be increased to 1 tablet twice a day if needed |
| Short term insomnia | 1 or 2 tablets (25mg to 50mg) as a single night time dose |
| Motion sickness prevention | 1 tablet (25mg) the night before a journey, repeated after 6 to 8 hours if required |
These are the doses listed for Phenergan 25mg tablets for adults and children over 10 years. Your own dose may be different depending on why you are taking it and your medical history.
Do not increase the dose yourself if you feel that the medicine is not working well enough. The patient information leaflet specifically advises speaking to a doctor or pharmacist rather than changing the dose yourself.
Can You Take 2 Phenergan Tablets?
For short term insomnia in adults, 2 Phenergan 25mg tablets, or 50mg, is within the dose listed in the UK product information. It is taken as a single dose at night.
However, that does not mean 2 tablets are appropriate for every situation. The dose for allergies and motion sickness is different.
If you normally take 1 tablet and are thinking about taking 2, check with your pharmacist or prescriber first, particularly if the higher dose has not been recommended for you.
What Is the Maximum Dose of Phenergan Tablets?
There is no single 100mg maximum that applies to all uses of Phenergan tablets.
For adults taking the 25mg tablets, the product information gives different maximums depending on the reason for treatment. For allergies, the dose can be increased to 25mg twice a day if required. For short term insomnia, the listed dose is 25mg or 50mg as a single dose at night. For motion sickness, 25mg can be repeated after 6 to 8 hours if required.
This is why it is not appropriate to use 100mg as a general daily limit for Phenergan tablets.
If you have taken more than the recommended dose, contact NHS 111 for advice even if you feel well. If you have breathing problems, a seizure, become unconscious, develop a very fast or irregular heartbeat, or have other serious symptoms, call 999 or go to A&E.
Is 100mg of Phenergan for Sleep Too Much?
Yes. 100mg is well above the 25mg to 50mg night time dose listed for short term insomnia in adults. It should not be used as a routine sleep dose.
If 25mg or 50mg is not helping you sleep, do not keep increasing the dose yourself. Speak to a pharmacist or doctor about what to do next.
Taking too much promethazine can cause serious effects, including severe drowsiness, changes in consciousness, seizures, an irregular heartbeat and, in overdose, breathing problems.
A Note on Phenergan Scheduling Outside the UK
This guide covers UK dosing and availability. The way promethazine is classified, supplied and used can differ between countries.
If you are asking about Phenergan in another country, such as South Africa, check with a local pharmacist or medicines regulator rather than assuming that UK guidance applies.
If you have questions about your own dose, a pharmacist can advise before you order Phenergan 25mg tablets.
Important Safety and Side Effects Information
- Phenergan 25mg tablets are not for children under 6 years of age. Promethazine can cause serious breathing and central nervous system effects in younger children.
- Phenergan should be avoided if you are taking an MAOI or have taken one within the previous 14 days.
- Tell your doctor or pharmacist about other medicines you take, especially sedatives, sleeping medicines, some antidepressants and medicines with anticholinergic effects. Phenergan can increase their effects.
- Do not use Phenergan for more than 7 days without seeking medical advice.
- Avoid alcohol while taking Phenergan because it can increase drowsiness and other sedating effects.
- Older adults may be more sensitive to the effects of promethazine and may need particular care with dosing.
- Common side effects can include dry mouth, blurred vision, constipation, dizziness and drowsiness.
- Promethazine can sometimes cause excitement, restlessness or unusual behaviour in children rather than making them sleepy.
- Do not drive, cycle or operate machinery if you feel sleepy, dizzy or have blurred vision. The effects of Phenergan can last for up to 12 hours.
Genuine Pricing
| Product | Price |
|---|---|
| Phenergan 25mg, 56 tablets | £14.99 |
| Phenergan Elixir 5mg/5ml, 100ml | £14.49 |
Medical Disclaimer
This page provides general information about adult Phenergan tablet dosing. It is not a substitute for personalised medical advice, diagnosis or treatment.
Do not increase your Phenergan dose yourself if you feel that the recommended amount is not working. The correct dose depends on why you are taking the medicine and your individual circumstances.
If you take more than the recommended dose, contact NHS 111 for advice even if you feel well. Call 999 or go to A&E if you develop serious symptoms such as breathing problems, a seizure, loss of consciousness or a very fast or irregular heartbeat.
Phenergan should not be used for longer than 7 days without medical advice. It can cause drowsiness, dizziness and blurred vision, so do not drive or operate machinery if you are affected.
If you are unsure about your dose, have taken more than recommended, or are taking other medicines that may interact with promethazine, speak to a pharmacist or GP.
