Phenergan is one of the UK medicines containing promethazine that is licensed for short term treatment of insomnia in adults. This is why searches such as "how much Phenergan for sleep" are common. Promethazine hydrochloride is used for several different reasons, including insomnia, allergies, travel sickness and nausea. The dose can therefore change depending on your age, the formulation and why you are taking it.
This guide explains the licensed Phenergan dosage for adults and children in these situations, based on the UK Summary of Product Characteristics (SmPC), the approved patient information leaflets and NHS medicines guidance. The doses below are reference information only and are not a personal prescription.
Quick Answer: Phenergan Dose for Sleep
For adults and children over 10 years, the licensed Phenergan dose for short term insomnia is 25mg or 50mg as a single dose at night. That is one or two 25mg tablets. Phenergan Elixir contains 5mg in each 5ml, although the product information recommends Phenergan tablets for adults and children over 10 for these doses.
Key takeaways
- The licensed adult night time range for sleep is 25mg to 50mg, taken once.
- 25mg is at the lower end of the licensed adult range. 50mg is the upper end, not a dose that everyone needs.
- Oral Phenergan is not for children under 6 years.
- Promethazine can cause drowsiness, dizziness and blurred vision. The duration of action may be up to 12 hours, so these effects can continue into the next day.
- Phenergan should not be taken for longer than 7 days without medical advice.
What Phenergan Is and How Promethazine Works
Phenergan is a brand of promethazine hydrochloride. Promethazine is a first generation, or sedating, antihistamine. NHS guidance explains that it blocks the effects of histamine, which helps relieve allergy symptoms and can also make you feel sleepy.
Promethazine also acts on other chemical signals in the brain. This is one reason it can be used for nausea, vomiting and motion sickness, as well as for its sedating effects.
How quickly it works and how long it lasts
NHS guidance says that promethazine can start working within around 20 minutes. For allergies, nausea and some other symptoms, the effects usually last around 4 to 6 hours. However, the Phenergan SmPC warns that its duration of action may be up to 12 hours, particularly when considering drowsiness, dizziness and blurred vision.
This is important if you take it at night. You may still feel sleepy or less alert the following morning, even if you feel that the main effect has worn off.
Phenergan Strengths and Formulations Available in the UK
Phenergan and other promethazine products are available in different strengths. The formulation affects how much medicine you can take in each dose.
| Formulation | Strength | Typical use | Legal status |
|---|---|---|---|
| Phenergan tablets | 25mg | Standard adult dosing for sleep, allergy and travel sickness | Pharmacy medicine (P), 56 tablet packs |
| Promethazine tablets | 10mg and 20mg | Lower strength options, including allergy treatment | Pharmacy medicine, availability varies |
| Phenergan Elixir | 5mg per 5ml | Oral liquid for children aged 6 and over and adults where appropriate | Pharmacy medicine |
| Phenergan Injection | 25mg per ml | Hospital and clinical settings | Prescription only medicine |
NHS guidance confirms that promethazine tablets are available in 10mg, 20mg and 25mg strengths and that the liquid contains 5mg in each 5ml.
Choosing between tablets and elixir
| Consideration | 25mg tablets | Elixir 5mg/5ml |
|---|---|---|
| Dose precision | Fixed 25mg dose | Can be measured in smaller amounts |
| Swallowing difficulty | May be a barrier | Suitable for people who cannot swallow tablets |
| Ages 6 to 10 | Licensed for some indications | Useful where a liquid dose is recommended |
| Measuring required | None | Use the supplied medicine spoon or oral syringe |
The elixir allows smaller doses to be measured than a 25mg tablet. Always use the measuring device supplied with the medicine. Do not use a kitchen teaspoon because it may not measure the correct amount.
Phenergan Dosage for Sleep
Short term insomnia in adults is a licensed indication for Phenergan. The licensed dose for adults and children over 10 is 25mg or 50mg as a single dose at night.
The product information also gives a 25mg night time dose for children aged 6 to 10 when Phenergan tablets are used as a short term paediatric sedative. This does not mean Phenergan should be used as a routine sleep aid for children. Any use in a child should be discussed with a doctor or pharmacist.
| Age group | Licensed night time dose for sleep or sedation | Source |
|---|---|---|
| Adults and children over 10 | 25mg or 50mg as a single night time dose | Phenergan 25mg tablets SmPC |
| Children 6 to 10, tablets | 25mg as a single night time dose | Phenergan 25mg tablets SmPC |
| Children 6 to 10, elixir | 20mg or 25mg as a single night time dose | Phenergan Elixir SmPC |
| Children under 6 | Not for use | Phenergan SmPC |
The Phenergan Elixir SmPC gives 20mg or 25mg for children aged 6 to 10 and recommends the tablets for adults and children over 10 when these night time doses are required.
Phenergan 25mg for sleep dosage
One 25mg tablet is at the lower end of the licensed adult range for short term insomnia. It may be suitable for some adults, but the right dose depends on the individual and why the medicine is being used.
Promethazine can make you drowsy, so it is important to take it only when you can allow enough time for sleep and when you do not need to drive or operate machinery afterwards.
Phenergan dose for sleep 50mg
50mg, or two 25mg tablets, is the upper end of the licensed single night time dose for adults and children over 10.
It is a maximum licensed dose for this indication, not a target dose. A higher dose is not automatically more suitable, and it may increase unwanted effects such as drowsiness, dizziness and blurred vision. The effects can last for up to 12 hours.
Phenergan dose for sleep 10mg
10mg is below the licensed Phenergan dose for short term insomnia in adults. Promethazine 10mg tablets are available in the UK and may be used for other indications, such as allergy symptoms.
If you are considering a lower dose because you are worried about next day drowsiness, ask a pharmacist or prescriber whether it is appropriate for you rather than changing the dose yourself.
Phenergan elixir dosage for sleep
Phenergan Elixir contains 5mg of promethazine in each 5ml.
For children aged 6 to 10, the licensed night time dose is 20mg or 25mg, which is 20ml or 25ml of the elixir.
For adults and children over 10, the licensed night time range is 25mg to 50mg, but the elixir product information recommends using Phenergan tablets for these doses.
Promethazine Dosage for Allergy Symptoms
Promethazine is licensed for the symptomatic treatment of allergic conditions affecting the upper respiratory tract and skin, including allergic rhinitis and urticaria.
| Age group | Formulation | Licensed allergy dose |
|---|---|---|
| Adults and children over 10 | 25mg tablets | 25mg as a single dose, increasing to a maximum of 25mg twice daily |
| Adults and children over 10 | Elixir 5mg/5ml | 10mg twice daily, increasing to a maximum of 20mg three times daily |
| Children 6 to 10 | 25mg tablets | 25mg as a single dose, maximum 25mg daily |
| Children 6 to 10 | Elixir 5mg/5ml | 10mg to 25mg as a single dose, or 5mg to 10mg twice daily, maximum 25mg daily |
NHS guidance gives similar adult doses for hay fever and hives, ranging from 10mg twice a day to 20mg three times a day, or 25mg once or twice a day.
Because promethazine is sedating, some people find that taking a dose later in the day is easier if they need to stay alert. However, the timing should follow the instructions for the product you are using.
Phenergan Dosage for Travel Sickness, Nausea and Vertigo
| Situation | Age group | Licensed or NHS stated dose |
|---|---|---|
| Preventing travel sickness | Adults and over 10 | 25mg the night before, repeated after 6 to 8 hours if needed |
| Short journey | Adults and over 10 | 25mg taken 1 to 2 hours before travelling, depending on the product |
| Treating travel sickness once it starts | Adults and over 10 | 25mg as soon as possible and 25mg the same evening, then 25mg the following evening if needed |
| Preventing travel sickness | Children 6 to 10, elixir | 10mg the night before, repeated after 6 to 8 hours if needed |
| Vertigo | Adults | 25mg a day, up to 25mg four times a day, according to NHS guidance |
NHS guidance gives 25mg up to 4 times a day as the adult range for vertigo. That is different from the dose used for sleep and should not be used as a general maximum for all reasons for taking promethazine.
Max Dose of Phenergan in 24 Hours
There is no single maximum promethazine dose for every situation. The licensed maximum depends on why it is being used and which formulation you are taking.
| Indication | Stated 24 hour maximum | Notes |
|---|---|---|
| Short term insomnia | 50mg | A single night time dose |
| Allergy, 25mg tablets | 50mg, 25mg twice daily | Per the 25mg tablet SmPC |
| Allergy, elixir | 60mg, 20mg three times daily | Per the elixir SmPC |
| Allergy, children 6 to 10 | 25mg | Per the SmPC |
| Vertigo | Up to 100mg | NHS stated range |
| Injection, adults | 100mg parenteral maximum | Clinical settings only |
For someone asking about the promethazine maximum dose, the answer depends on the reason for taking it. For sleep, the licensed maximum is 50mg as one night time dose. For allergy, the maximum is 50mg with the 25mg tablets or 60mg with the elixir.
Do not take more than the recommended dose. Taking too much promethazine can be dangerous. NHS guidance advises contacting 111 even if there are no symptoms after taking more than the recommended dose. Call 999 or go to A&E if there are breathing problems, a seizure, loss of consciousness, a very fast or irregular heartbeat, or hallucinations.
Phenergan Dose Per kg: Why UK Dosing Is Age Banded
Weight based dosing is used for some medicines in children, so looking for a Phenergan dose per kg is understandable. For oral Phenergan in the UK, however, the licensed doses are given by age group and indication rather than as a general mg per kg schedule.
The UK product information does not provide a general oral mg per kg dose for parents to calculate at home. If a child needs a dose based on their weight, this should be worked out by a doctor or pharmacist using the appropriate clinical information.
Age Restrictions and Children
- Oral Phenergan is not for children under 6 years, according to the Phenergan tablet and elixir product information.
- Phenergan Injection is not for children under 2 years because of the risk of serious respiratory effects.
- NHS guidance says cough and cold medicines containing promethazine should not be given to children aged 5 or under.
- Children aged 6 to 10 have specific licensed doses for some indications. The elixir can be useful because it allows the dose to be measured accurately.
- Short term sedation is a licensed use for some children aged 6 years and over, but this does not make promethazine a routine sleep medicine for children.
If you are considering promethazine for a child, check the exact product and indication with a doctor or pharmacist. Different promethazine products can have different age restrictions and instructions.
How Long Can You Take Phenergan For?
The Phenergan patient information leaflet says not to take the medicine for longer than 7 days without speaking to a doctor. NHS guidance also recommends using promethazine for a short time unless a doctor advises otherwise.
There are several reasons to review longer use:
- Tolerance. If promethazine is used regularly, its effect can become less noticeable for some people.
- Stopping after long term use. NHS guidance says that people who have taken promethazine for a long time and then stop suddenly may experience symptoms such as dizziness, sweating, nausea, a racing heart and difficulty sleeping. Coming off it gradually may help prevent these symptoms.
- The reason for poor sleep. If insomnia continues, it is worth looking at what may be causing it rather than simply continuing a sedating medicine.
NHS guidance says it is unlikely that people will become addicted to promethazine, but it is still intended for short term use unless a doctor advises otherwise.
Where Phenergan Fits Alongside NHS and NICE Insomnia Guidance
The NHS advises that most adults need around 7 to 9 hours of sleep. If sleep problems continue, it is worth discussing them with a GP rather than relying on a sedating antihistamine for a long period.
For ongoing insomnia, treatment can include sleep advice and cognitive behavioural therapy for insomnia, known as CBT I. NICE guidance describes CBT I as an important treatment approach for persistent insomnia. Medicines used for sleep are generally considered for short periods and should be reviewed.
NICE Technology Appraisal TA77 discusses the short term use of licensed hypnotic medicines for insomnia and stresses the importance of considering non drug measures. TA77 does not specifically cover promethazine, so it should not be treated as a direct recommendation for Phenergan.
Who Should Not Take Promethazine
Contraindicated
- Known hypersensitivity to promethazine or other phenothiazines
- Coma or central nervous system depression from any cause
- Children under 6 years for oral Phenergan
- People taking, or who have recently taken, a monoamine oxidase inhibitor (MAOI) within the previous 14 days
Use only after medical advice or with particular caution
- Liver or kidney problems
- Parkinson's disease
- Myasthenia gravis
- Heart problems, including some conditions that can affect heart rhythm
- Narrow angle glaucoma
- Epilepsy or other seizure conditions
- An enlarged prostate, difficulty passing urine or urinary retention
- Asthma, bronchitis or bronchiectasis, because promethazine can thicken or dry lung secretions and make them harder to clear
- Medicines that can prolong the QT interval
- Other sedatives, sleeping medicines, some antidepressants and medicines with anticholinergic effects
- Pregnancy or breastfeeding
- Older adults, who may be more likely to experience anticholinergic side effects and confusion
If you are taking other medicines, check with a pharmacist or doctor before taking promethazine. It can increase the effects of some medicines, particularly other medicines that cause drowsiness.
If you have a skin prick allergy test booked, tell the clinic that you take promethazine. It can affect the result, and the Phenergan SmPC advises stopping it at least 72 hours before skin testing.
Side Effects, Alcohol and Driving
Drowsiness is a very common effect of promethazine. This may be useful when it is taken for sleep but can be a problem when you need to stay alert. Other possible effects include dry mouth, blurred vision, dizziness and constipation.
Alcohol should be avoided while taking promethazine because it can increase its sedative effects.
Do not drive or use machinery if you feel sleepy, dizzy, confused or unable to concentrate. The Phenergan SmPC states that the duration of action may be up to 12 hours, so these effects can continue into the following morning.
Buying Phenergan in the UK: Legal Status, Cost and What to Check
Phenergan 25mg tablets are classified as a pharmacy medicine (P), which means they are supplied through a pharmacy under the supervision of a pharmacist. The exact availability and pack size can vary.
Buying medicines online can be legitimate when you use a properly registered pharmacy. Before ordering, check that the pharmacy is registered and that the service carries out the appropriate checks before supplying the medicine.
Phenergan prices at EveryDayMeds
| Product | Pack size | Price | Approximate cost per dose |
|---|---|---|---|
| Phenergan 25mg tablets (promethazine hydrochloride) | 56 tablets | £14.99 | About £0.27 per 25mg tablet |
| Phenergan Elixir 5mg/5ml | 100ml | £14.49 | About £3.62 per 25mg, 25ml dose |
These are the standard list prices shown on our product pages and exclude promotional codes. Check the current listings for Phenergan 25mg tablets and Phenergan Elixir 5mg/5ml before ordering, as prices and availability can change.
Questions to ask before buying promethazine online
- Is the seller a registered pharmacy? Check the pharmacy's registration details with the General Pharmaceutical Council.
- Is there a clinical check? An online pharmacy should have an appropriate process for assessing whether a medicine is suitable before supplying it.
- Is the price the total price? Check whether delivery, packaging or consultation fees are added at checkout.
- Is it UK sourced and in date? Check the product details, expiry information and sourcing if these details are not clear.
What happens after you order
Orders are reviewed against a suitability questionnaire before dispatch, where required, and then packed and sent according to the pharmacy's delivery process.
For Phenergan Elixir, the product information says to store it below 25°C, keep it in the outer carton to protect it from light and use it within 1 month of opening. Keep medicines out of the sight and reach of children and return unused medicine to a pharmacy for safe disposal.
Things to Know Before Your First Dose
- Take a night time dose only when you can allow enough time for sleep and when you will not need to drive or operate machinery afterwards.
- If you are taking it for sleep, follow the dose on the product information or the advice given by your pharmacist or doctor.
- Keep the next morning as clear as possible the first time you take it, so you can see how strongly it affects you.
- Swallow tablets whole with water. For the elixir, use the supplied medicine spoon or an oral syringe rather than a kitchen spoon.
- If you forget a dose for sleep or sedation, skip it and take the next dose at the usual time. Do not take 2 doses together.
- The licensed adult dose for short term insomnia is 25mg to 50mg as a single night time dose. If you are unsure whether this is suitable for you, ask a pharmacist or prescriber.
Medical Disclaimer
This Phenergan dosage guide was compiled by the EveryDayMeds editorial team using the UK Summary of Product Characteristics for Phenergan 25mg tablets, Phenergan Elixir and Phenergan Injection, the approved patient information leaflets, NHS medicines guidance and relevant NICE guidance. It describes licensed UK dosing and general medicine information for reference only. It is not a recommendation to take promethazine at any particular dose. Always follow the instructions supplied with your medicine and speak to a pharmacist or doctor if you are unsure whether promethazine is suitable for you.
