For everyday allergy symptoms, cetirizine is one of the non drowsy antihistamines commonly recommended as a first choice in the UK. NICE guidance recommends a non sedating antihistamine for conditions such as allergic rhinitis and urticaria, while first generation antihistamines are generally not preferred for routine allergy treatment because they can cause drowsiness and affect concentration.
That does not mean Phenergan is a poor medicine. Phenergan contains promethazine, a sedating antihistamine that is also used for problems cetirizine does not treat, including motion sickness and, in some formulations, short term insomnia. In those situations, its sedating effect can be part of the reason it is used. The two medicines are better thought of as options for different situations rather than direct rivals.
Key things to know
- Phenergan is a brand of promethazine hydrochloride, a first generation sedating antihistamine. Cetirizine is generally classed as a second generation, non drowsy antihistamine, although it can still make some people sleepy.
- For hay fever, allergic rhinitis and hives, non sedating antihistamines such as cetirizine are generally preferred for routine treatment.
- Drowsiness is a common side effect of promethazine and can last for several hours. Cetirizine is less likely to cause sleepiness, but some people still feel tired or sleepy after taking it.
- Adults usually take cetirizine once a day. Promethazine dosing depends on what it is being used for and can involve one or more doses a day.
- Phenergan 25mg tablets and Phenergan Elixir are not for children under six. Other promethazine products can have different age restrictions.
- If a medicine makes you sleepy, dizzy or affects your concentration, do not drive or use machinery. This can also have legal implications in the UK.
Is Phenergan and promethazine the same thing
Yes. Phenergan is a brand name, while promethazine hydrochloride is the active ingredient in Phenergan.
This means searches such as promethazine vs cetirizine, promethazine hydrochloride vs cetirizine, cetirizine vs promethazine, cetirizine vs Phenergan and Phenergan vs cetirizine are generally comparing the same two active medicines.
What is cetirizine, then, and what is cetrizine when people spell it that way? Cetirizine hydrochloride is an antihistamine used for conditions such as hay fever, other allergies and hives. It is available from pharmacies and shops in the UK, as well as on prescription.
The core difference between promethazine and cetirizine
The main difference between promethazine and cetirizine is how they affect the brain as well as their use in different situations.
Promethazine is a first generation, sedating antihistamine. It can enter the brain more readily, which helps explain why it can cause sleepiness, dizziness and difficulty concentrating. It also has anticholinergic effects, which can include dry mouth, blurred vision and difficulty passing urine.
Cetirizine is generally classed as a second generation, non drowsy antihistamine. It is much less likely to make you sleepy than some older antihistamines, although drowsiness can still happen. It is used for allergy symptoms such as sneezing, a runny or blocked nose, itchy or watery eyes, and hives.
So, is cetirizine like promethazine? Both are antihistamines and both block the effects of histamine. However, they can feel quite different because promethazine is much more likely to cause drowsiness.
Both medicines can interact with other medicines. Promethazine has a number of important interactions, including with some antidepressants, opioids, medicines that cause drowsiness and some medicines used for heart problems or epilepsy. Ask a pharmacist or doctor if you take other medicines regularly.
Alcohol should be avoided with promethazine because it can increase its sedating effects. If cetirizine makes you sleepy, alcohol may also make this worse.
If you develop a severe allergic reaction, such as difficulty breathing or swelling of the face, mouth or throat, seek emergency medical help. For other troublesome or unusual symptoms, speak to a pharmacist or doctor.
Pregnancy is another situation where the choice should be considered carefully. NHS guidance states that cetirizine can be taken during pregnancy, while the product information for Phenergan advises that it should not normally be used during pregnancy unless the potential benefits outweigh the potential risks. If you are pregnant or trying to become pregnant, ask your doctor or pharmacist which option is appropriate for you.
There is usually no need to stop either medicine under medical supervision simply because you have taken it for a short period. If you have been taking cetirizine regularly for a long time, NHS guidance advises speaking to your doctor before stopping it. With either medicine, ask a healthcare professional if you are unsure about changing or stopping treatment.
| Feature | Phenergan (promethazine) | Cetirizine |
|---|---|---|
| Generation | First | Second |
| Sedation | More likely to cause drowsiness | Less likely to cause drowsiness, but sleepiness can still happen |
| Duration | Drowsiness can last for several hours | Usually taken once daily in adults |
| Dosing pattern | Depends on why it is being used | Usually once daily in adults |
| Anticholinergic effects | Yes, including dry mouth and blurred vision | Much less prominent |
| Licensed uses | Allergies, nausea and vomiting, motion sickness and short term insomnia in adults, depending on the product | Allergies and hives, among other allergic conditions |
| Minimum age | Phenergan 25mg tablets and Elixir: six years | Depends on the product and age |
| Legal category | Pharmacy medicine | General sale or pharmacy medicine, depending on the product |
Which one is more effective
This depends on what you are taking it for.
For routine allergy symptoms, UK guidance generally favours a non sedating antihistamine such as cetirizine. For allergic rhinitis, treatment can also include a steroid nasal spray when symptoms are more troublesome or persistent, particularly when nasal congestion is a major problem. For urticaria, NICE recommends a non sedating antihistamine at the standard licensed dose.
So, is cetirizine good for allergies? Yes. It is a commonly used option for hay fever, allergic rhinitis and hives.
Does that make Phenergan ineffective for allergies? No. Promethazine is also licensed for allergic conditions, including allergic rhinitis and urticaria. The reason it is usually not the first choice for routine allergy treatment is mainly its sedating and anticholinergic effects, rather than a lack of antihistamine activity.
Sedation, driving and next day impairment
This is one of the biggest practical differences between the two medicines.
Promethazine commonly causes daytime drowsiness. NHS guidance says this drowsiness usually wears off within 12 hours, although people can respond differently. It can also cause dizziness, unsteadiness and difficulty concentrating.
Cetirizine is classed as a non drowsy antihistamine, but it can still make some people feel sleepy or tired. If this happens, you should not drive, cycle or use tools or machinery until you feel able to do so safely.
In the UK, driving while your ability is affected by a medicine can be a legal issue as well as a safety concern. If you drive for work, operate machinery or need to stay alert, it is worth considering how an antihistamine affects you before deciding when to take it.
When promethazine still has the advantage
Cetirizine cannot be used for every reason that promethazine is used.
Motion sickness is one clear example. Promethazine can be used to prevent or treat motion sickness, while cetirizine is an allergy medicine and is not used for travel sickness. Promethazine dosing for motion sickness is different from its dosing for allergies, so follow the instructions for the specific product you are using.
Cinnarizine vs promethazine is a more relevant comparison when you are looking specifically at medicines for motion sickness and vertigo. Both can cause drowsiness, so a pharmacist can help you choose an option based on your symptoms, other medicines and how much you need to stay alert.
Short term insomnia is another difference. Phenergan 25mg tablets are licensed for short term treatment of insomnia in adults, with the product information listing a single night time dose of 25mg or 50mg. Cetirizine is not a sleep medicine.
Promethazine can also be used when allergy symptoms are keeping someone awake, but its sedating effect needs to be considered. It is not generally a medicine to take every night throughout a hay fever season. Phenergan should not be used for longer than 7 days without medical advice.
Safety differences that matter more than sedation
Promethazine has some restrictions and precautions that are worth knowing before you take it.
- Phenergan should be avoided if you are taking, or have taken within the previous 14 days, a monoamine oxidase inhibitor (MAOI) antidepressant. If you are unsure whether your antidepressant is an MAOI, check with a pharmacist or doctor.
- Phenergan 25mg tablets and Phenergan Elixir are not for children under six. Other promethazine products can have different age restrictions, so always check the specific product.
- Phenergan should not be used by people in a coma or with central nervous system depression, or by people who are allergic to promethazine or other phenothiazines.
- Tell your doctor or pharmacist if you have epilepsy, asthma or another breathing problem, liver or kidney problems, Parkinson's disease, an underactive thyroid, heart problems, myasthenia gravis, an enlarged prostate or narrow angle glaucoma.
- Older adults may be more sensitive to some of the sedating and anticholinergic effects of first generation antihistamines. A pharmacist or doctor can help you choose the most suitable option.
- Phenergan should not be used for longer than 7 days without medical advice.
Cetirizine has fewer restrictions for most people, but it may not be suitable for everyone. People with kidney problems may need a lower dose, and people with epilepsy, difficulty passing urine or certain allergies should check with a doctor or pharmacist before taking it.
If you are unsure which antihistamine is suitable for you, our clinical team page explains who reviews queries and how to get advice.
How the other antihistamines compare
Several other names come up in searches for Phenergan and cetirizine. Here is a simple way to see where they fit.
| Medicine | Generation | Sedating | Mainly used for |
|---|---|---|---|
| Cetirizine | Second | Less likely to cause drowsiness | Hay fever, allergies, hives |
| Loratadine | Second | Less likely to cause drowsiness | Hay fever, allergies, hives |
| Fexofenadine | Second | Less likely to cause drowsiness | Hay fever, allergies, hives |
| Acrivastine | Second | Can cause drowsiness | Hay fever and other allergies |
| Chlorphenamine (Piriton) | First | Yes | Allergies and allergic reactions |
| Promethazine (Phenergan) | First | Yes | Allergies, motion sickness and short term insomnia |
| Cinnarizine | First | Yes | Motion sickness and vertigo |
Fexofenadine vs Phenergan, or Phenergan vs fexofenadine, is another comparison between a less sedating antihistamine and a more sedating one. Fexofenadine is generally less likely to cause drowsiness than many other antihistamines, although sleepiness can still happen. It also has an important food and drink interaction: apple, orange and grapefruit juice can reduce how well it works, so tablets should be taken with water.
Difference between Piriton and cetirizine, and chlorphenamine vs cetirizine, is mainly the difference between a sedating first generation antihistamine and a less sedating second generation option. Chlorphenamine can cause sleepiness, dizziness and difficulty concentrating and usually needs to be taken several times a day.
Chlorphenamine is also sometimes used in specific situations during breastfeeding. Current NHS Specialist Pharmacy Service guidance considers chlorphenamine the preferred sedating antihistamine when a sedating option is needed, while cetirizine and loratadine are preferred non sedating options. This does not mean one medicine is automatically right for everyone.
Brand names that differ by country
Some of the confusion around these medicines comes from brand names that contain different active ingredients in different countries.
- Zyrtec is a brand name for cetirizine in the United States and some other countries. So Phenergan vs Zyrtec, promethazine vs Zyrtec, and Zyrtec and Phenergan are generally the same comparison as this page. In the UK, cetirizine is sold under names such as Zirtek, Piriteze and some Benadryl products, as well as under the generic name cetirizine.
- Benadryl can mean different antihistamines depending on the country. In the United States, Benadryl commonly contains diphenhydramine. In the UK, Benadryl Allergy contains acrivastine, so it is a different comparison. Always check the active ingredient on the pack rather than relying on the brand name.
- Allergex is a brand name used for chlorphenamine in some countries, including South Africa. Phenergan vs Allergex is therefore a comparison between promethazine and chlorphenamine, both of which are sedating antihistamines.
- Avil is a brand name used for pheniramine in India and some other countries. It is not a UK brand, so Avil vs Phenergan is a comparison between two different first generation antihistamines.
Alternatives to Phenergan
The best alternative depends on why you are taking Phenergan. There is no single replacement that suits every situation.
| What you need it for | Alternatives worth asking about |
|---|---|
| Hay fever and allergic rhinitis | Cetirizine, loratadine or fexofenadine. A steroid nasal spray may also help, particularly when nasal congestion is a major symptom |
| Hives and itching | A non sedating antihistamine such as cetirizine, loratadine or fexofenadine may be preferred for regular allergy symptoms |
| Motion sickness | Cinnarizine or hyoscine may be options to discuss with a pharmacist before travelling |
| Short term sleep difficulty | Sleep habits and a conversation with a pharmacist or doctor about whether a medicine is appropriate |
| Night time allergy symptoms | Treating the allergy itself with a suitable antihistamine or other allergy treatment, rather than relying on sedation |
If your symptoms are not improving, keep coming back or need daily treatment for months, it is worth speaking to a GP or pharmacist. You may need a different type of treatment rather than simply switching to another antihistamine.
Cost and availability
Both medicines are widely available in the UK, but the price depends on the product, pack size and pharmacy.
| Product | Pack | Price |
|---|---|---|
| Phenergan 25mg tablets | 56 tablets | £14.99 |
| Phenergan Elixir 5mg/5ml | 100ml oral solution | £14.49 |
Prices shown were correct at the time of writing. Always check the live product page for the current price and availability.
Cetirizine is also widely available from pharmacies and shops, often as a low cost generic medicine. For straightforward hay fever or other allergy symptoms, the choice is usually more about the type of symptoms you have and whether you need to avoid drowsiness than about price.
Phenergan is a pharmacy medicine, so it is supplied under the supervision of a pharmacist. This can be useful if you are unsure which antihistamine is right for you, particularly if you take other medicines or have an existing health condition. You can reach the team through our contact page if you want to check something before ordering.
Medical Disclaimer
This page provides general information about Phenergan, promethazine and cetirizine in the UK. It is not medical advice, a diagnosis or a substitute for advice from a pharmacist, GP or another qualified healthcare professional who knows your medical history.
No individual dose is recommended here. Always follow the instructions on your medicine's packaging and patient information leaflet. If you are unsure how or when to take your medicine, ask a pharmacist. Do not exceed the stated dose or add another antihistamine unless a healthcare professional has advised you to do so. Phenergan should not be used for longer than seven days without medical advice.
References to NICE Clinical Knowledge Summaries and NHS guidance describe general treatment approaches. They do not mean that a particular medicine is right for everyone. The most suitable antihistamine can depend on your symptoms, other medicines you take, existing health conditions and whether you need to stay alert during the day.
Tell your pharmacist or doctor about other medicines you take, including medicines bought without a prescription. It is also useful to mention if you are pregnant or breastfeeding, or if you have conditions such as epilepsy, glaucoma, prostate problems, liver or kidney problems. Tell them if you have recently taken an MAOI antidepressant, as this can affect whether promethazine is suitable for you.
If you think you are having a serious allergic reaction, such as swelling of the face, lips or throat or difficulty breathing, seek urgent medical help. Suspected side effects from medicines can also be reported through the MHRA Yellow Card scheme.
