Antihistamine brand names can be confusing because the same brand name may contain different medicines in different countries. A name you recognise from abroad or online, such as Restavit, Allergex, Polaramine or Avil, may not contain the ingredient you expect.
If you searched for "Phenergan vs Benadryl", the answer depends on where you are. Phenergan contains promethazine. In the UK, Benadryl contains acrivastine, a non drowsy antihistamine. In the US, Benadryl usually contains diphenhydramine, which is a sedating antihistamine. Diphenhydramine and promethazine can both cause drowsiness, but they are different medicines.
This guide is for adults in the UK who want to understand common antihistamine brands and how they compare with Phenergan. We look at the active ingredient in each medicine, where the brands are used, possible UK equivalents, common uses and important safety points. If you have a medicine from another country, always check the active ingredient rather than relying on the brand name alone.
The One Rule: Check the Ingredient, Not the Brand
The most useful thing to remember is to check the active ingredient, not just the brand name.
A familiar brand can contain a different medicine depending on the country where it is sold. Equally, two different brand names can contain medicines from the same drug family.
If you have bought or been given an antihistamine abroad, check the packaging for the active ingredient before comparing it with a UK medicine. If you are unsure, a pharmacist can help you identify it.
The Brands at a Glance
| Brand | Active ingredient | Where sold | UK equivalent |
|---|---|---|---|
| Phenergan | Promethazine | UK and other countries | Phenergan |
| Restavit | Doxylamine | Australia | No direct UK equivalent |
| Allergex | Chlorphenamine | South Africa | Piriton |
| Polaramine | Dexchlorphenamine | Australia, Europe and other countries | No direct equivalent |
| Avil | Pheniramine | India and other countries | No direct UK equivalent |
| Benadryl (UK) | Acrivastine | UK | Benadryl |
| Benadryl (US) | Diphenhydramine | US | Some diphenhydramine products are sold in the UK, such as Nytol |
Phenergan vs Restavit
Restavit is an Australian brand containing doxylamine, a sedating antihistamine used for short term sleep problems.
So, Phenergan versus Restavit is really a comparison between promethazine and doxylamine. Both can cause drowsiness, but they are different medicines.
Promethazine is also used for problems such as nausea and motion sickness, while doxylamine is mainly used for its sedating effects in products where it is licensed for sleep.
Restavit is not a UK product. If you have used it abroad and want to know which UK medicine may be suitable for you, speak to a pharmacist rather than trying to match the brand name yourself.
Phenergan vs Allergex
Allergex is a South African brand containing chlorphenamine, a sedating antihistamine. In the UK, chlorphenamine is available in products such as Piriton.
So, Phenergan versus Allergex is a comparison between promethazine and chlorphenamine. Both are older, sedating antihistamines, but they are different medicines.
Chlorphenamine is used for allergy symptoms, while promethazine has several uses, including short term treatment of insomnia in adults.
If you have used Allergex abroad, check that the active ingredient is chlorphenamine before looking for a UK equivalent. A pharmacist can help you choose an appropriate product.
Phenergan vs Polaramine
Polaramine contains dexchlorphenamine, an antihistamine related to chlorphenamine. It is available in some countries but is not a standard UK product.
So, Phenergan versus Polaramine is a comparison between promethazine and dexchlorphenamine. They belong to different antihistamine groups and are different medicines.
If you have used Polaramine abroad, do not assume that another brand with a similar name will contain the same ingredient. Check the packaging or ask a pharmacist about the active ingredient and any suitable UK alternative.
Phenergan vs Avil
Avil is a brand containing pheniramine and is used in India and some other countries. It is not marketed as a standard tablet in the UK.
So, Phenergan versus Avil is a comparison between two different sedating antihistamines. They are not the same medicine and should not be treated as direct substitutes.
If you have used Avil abroad and need an antihistamine in the UK, speak to a pharmacist. They can check the ingredient in your Avil product and help you understand which UK medicine may be appropriate.
Phenergan vs Doxylamine
Doxylamine is a sedating antihistamine that is used in some countries for short term sleep problems. It is sold under brand names such as Unisom in the US and Restavit in Australia.
In the UK, doxylamine is available with vitamin B6 in Xonvea for pregnancy sickness. It is not generally sold as a standalone sleep tablet.
Phenergan and doxylamine can both cause drowsiness, but they are different medicines and have different licensed uses. Promethazine is also used for nausea and motion sickness, while doxylamine is mainly used for its sedating effects in products where it is licensed for sleep.
If you are considering either medicine, check the product information and speak to a pharmacist if you are unsure which one is suitable.
Is Promethazine the Same as Benadryl?
No. Promethazine and diphenhydramine are different medicines, although both can cause drowsiness.
The important point is that Benadryl does not contain the same ingredient in every country.
In the US, Benadryl usually contains diphenhydramine, a sedating antihistamine. In the UK, Benadryl contains acrivastine, which is a non drowsy antihistamine used for allergy symptoms.
This means that "Phenergan vs Benadryl" can mean two very different comparisons depending on where the Benadryl was bought.
Diphenhydramine and promethazine can both make you feel sleepy, but their effects and how long they last can differ between people. Do not assume that one dose of one medicine is equivalent to a dose of another.
Always check the active ingredient on the packaging before comparing medicines or taking a product bought abroad.
What This Means If You Are in the UK
The main takeaway is simple: do not use a foreign brand name to decide which UK medicine to buy.
Brands such as Restavit, Allergex, Polaramine and Avil are not standard UK products, and the same brand name may not contain the same ingredient in every country. It is also best not to buy unlicensed medicines from overseas without checking that they are appropriate and legally supplied.
In the UK, sedating antihistamines include promethazine, diphenhydramine and chlorphenamine. Promethazine is found in Phenergan, diphenhydramine is found in products such as Nytol, and chlorphenamine is found in products such as Piriton.
Promethazine is also included in some combination products used for cold and flu symptoms, such as Night Nurse. For allergy symptoms, non drowsy antihistamines available in the UK include cetirizine, loratadine and fexofenadine.
If you have used a particular antihistamine abroad and want to know what the UK equivalent might be, take the packet or a clear photo of the ingredients to a pharmacist. They can help you identify the medicine and explain your UK options.
Safety Points: Can You Drink Alcohol?
Sedating antihistamines such as promethazine and diphenhydramine can cause drowsiness. Alcohol can add to these effects, so it is best to avoid drinking alcohol while taking them.
Do not give promethazine to children under 6 for the uses covered by products with this age restriction, and do not use sedating antihistamines to make a child sleep. Promethazine also has important warnings for very young children, so always follow the age restrictions and product information for the medicine you have.
Do not take promethazine within 14 days of taking an MAOI antidepressant unless a doctor has specifically advised you to do so.
If you are using Phenergan for sleep, it is intended for short term use. Do not continue taking it for more than 7 days without medical advice.
Sedating antihistamines can make you sleepy or less alert, and these effects can continue into the following day in some people. Do not drive, cycle or operate machinery if you feel drowsy or less alert.
Check with a pharmacist or doctor before taking promethazine if you are older, pregnant, planning a pregnancy or breastfeeding, or if you have asthma or other breathing problems, glaucoma, an enlarged prostate, or liver or kidney problems.
You should also check before taking it if you use other medicines, particularly medicines that can cause drowsiness. Some cough, cold and pain medicines can contain antihistamines or other ingredients that cause drowsiness, so check the ingredients before combining products.
If you are unsure whether a particular antihistamine is suitable for you, a pharmacist can check your medicines and any relevant health conditions.
