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Will Promethazine For Sleep Improve My Sleep Quality?

a profile image of TSA author Alex

Written By Alex Petrović

Certified Sleep Consultant


10 June 2024 9 min read

These days, a lot people talks about promethazine syrup that they take for cough issues. The interesting thing is that they reported they slept well after taking it. Can you take promethazine for sleep? Let's find out!

Promethazine is most commonly used as an antihistamine, but it also has sedative effects. This means that, in theory, it can be used to treat both allergies and insomnia. But, is that really the case? Can you use promethazine for sleep aid?
Well, it would be easy to say both yes and no, but the truth is much more complicated. Therefore, we're going to take a good look at promethazine, all of its effects, and see just how effective it is (or isn't) when it comes to improving your sleep quality.

What is promethazine?

Promethazine is an antihistamine medication that is most commonly used to treat allergies. However, as we've said, promethazine has sedative effects. This means that it can make you drowsy and help you fall asleep. In addition, promethazine can also reduce the number of times you wake up during the night.

An image of a teaspoon of cough syrup.

Promethazine works by blocking histamine receptors. A substance called histamine is released by your body in response to an allergic reaction. When histamines attach to histamine receptors, they cause allergy symptoms such as itching, sneezing, and/or a runny nose. By blocking histamine receptors, promethazine prevents these symptoms from occurring.

On that note, promethazine is used for:

How different is promethazine from other cough syrups?

Promethazine is a phenothiazine derivative that differs structurally from antipsychotic phenothiazines by having a branched side chain and no ring replacement. It is assumed to be less dopamine antagonist-like as a result of this structure.

Promethazine is an H1 receptor blocking agent. In addition to antihistamine effects, it provides clinically beneficial sedative and antiemetic effects – unlike many other cough syrups.
But, if we're directly comparing it to some other common antihistamines like cetirizine, fexofenadine or loratadine, the difference between them would simply lie in their sedating effects.

An image of a man taking cough syrup while covered with a blanket

What is the time window of the promethazine effect?

Promethazine is well absorbed from the gastrointestinal tract and its effects are visible within 20 minutes after oral administration and usually last four to six hours, although they can last up to 12 hours. This makes it an ideal choice for the treatment of conditions such as nausea, which tend to be short-lived.

How long should I take promethazine?

Generally speaking, promethazine is not a long-term solution. it's a short-term therapy. The usual course of treatment is 7 to 10 days.

However, your doctor (or pharmacist) may recommend a longer course of treatment if your symptoms or problems are severe and require prolonged treatment.

When is the best time to take promethazine?

It depends on what you're taking it for.

If you're taking promethazine in order to get a good night's sleep, it's recommended that you take it 20 to 30 minutes before you go to bed.

On the other hand, if you're taking it to prevent motion sickness, you'll be better off taking it an hour or even two before a short trip, or a night before a long journey.

Can I develop an addiction to promethazine?

Promethazine isn't addictive, even though it is not recommended that you take it for a long period of time. Of course, if your doctor prescribes a long-term treatment, you shouldn't stop taking it until they tell you to do so.

While not addictive, it is possible that you'll experience some side effects after you stop taking promethazine after prolonged use.

The common side effects include


Does promethazine have any side effects?

Just like any other medication, promethazine also comes with an array of possible side effects – although rare.

The most common ones are:

Other potential side effects include:

An image of a young woman suffering from vertigo.

Serious side effects are rare but can occur. If you experience any of the following, call your doctor immediately:

Also, promethazine is not to be taken if you're suffering from any of the following conditions:

Is promethazine safe for pregnant women?

In a word – yes. Promethazine (the usual dose) is considered safe for pregnant women, as there is no evidence that suggests it causes any harm to the developing baby.

There are no reports of any adverse effects on the developing fetus when promethazine is used during pregnancy. However, as with any medication, it's always best to check with your doctor before taking anything – just to be on the safe side.

The same goes for breastfeeding. If your baby is healthy, there's no need to worry about promethazine passing into their system through your breast milk and causing any issues. However, as always, it's best not to use it for an extended period of time.


Is it safe to take promethazine with painkillers?

Yes, it is safe to take promethazine with painkillers. In fact, promethazine is often used in combination with other medicines (most commonly paracetamol) to treat conditions such as migraines and tension headaches.

One thing to remember is – if you're taking promethazine mixed with paracetamol and you're taking paracetamol as a painkiller, you should err on the side of caution and watch your dose carefully. Drug interactions are a serious thing. The absolute maximum of paracetamol you should take in a day is 4000mg spread across four 1000 mg doses.

Is it safe to take promethazine and drive a car?

No, it's not safe to take promethazine and drive a car. Promethazine can cause drowsiness, and operating a vehicle while drowsy can be extremely dangerous. If you have to take promethazine and drive, make sure you allow yourself plenty of time to rest before getting behind the wheel.

Is it safe to drink alcohol while taking promethazine?

No, it's not safe to drink alcohol while taking promethazine. Promethazine can cause drowsiness, and alcohol can amplify this effect. What could also happen is your breathing could end up affected and you might experience difficulties waking up.

avoid alcohol on a plane

How does promethazine help you sleep better?

A medicine called promethazine hydrochloride Phenergan night time tablets can help induce sleep. One or two tablets can be taken as a single dose approximately 20 minutes before going to sleep. Since this is over-the-counter medicine, make sure to let the pharmacist know whether you've taken any medicaments (including herbal medicines).

As far as how it all works – we've gone over it already. Promethazine can cause drowsiness. This is the main reason why it's used as a sleep aid. It helps to slow down the activity of the brain and central nervous system (which is how it helps with nausea), which in turn can make falling asleep easier.

How to dose promethazine properly?

The only way to properly dose promethazine is to consult with a healthcare professional and have them prescribe the correct dosage for you – even if you're taking Phenergan night time OTC drug.

This is because promethazine dosages can vary depending on the individual and their specific situation. For example, people who suffer from motion sickness or nausea may require a different dose than those who are using it as a sleep aid.

However, there are some general rules as to how much promethazine one might take depending on the issue their treating.

For example:

20-50 mg for insomnia at night

Insomnia is a sleep disorder that can make it difficult to fall asleep, stay asleep, or get restful sleep. Thankfully, promethazine might help.

Taking up to 50 mg for insomnia should be more than enough to help you fall and stay asleep.

10-20 mg twice a day for a hay fever

Hay fever, also known as allergic rhinitis, is a condition that causes inflammation and irritation in the nose. This is typically caused by an allergic reaction to things like pollen, dust mites, or animal dander.

If you're taking promethazine for hay fever, the general rule of thumb is to take 10-20 mg twice (sometimes thrice) a day.

10 mg twice a day for hives

Hives, also known as urticaria, are a type of skin rash that is characterized by itchy, red welts. They can vary in size and can appear anywhere on the body.

The standard dose of promethazine for hives is 10 mg twice a day.

25 mg 1-2 hours prior to a journey to prevent motion sickness

When travelling, some people may experience motion sickness. This can cause nausea, vomiting, and dizziness.

If you're susceptible to motion sickness, taking 25 mg of promethazine 1-2 hours before your journey can help prevent these symptoms. If you're going on a long journey, you could go with 50 mg the night before.

25mg 4 times a day for vertigo problems

Vertigo is a type of dizziness that is often accompanied by a feeling of spinning or rotation. It can be caused by a number of things, including inner ear problems or migraines.

For vertigo, the standard dose of promethazine is 25 mg 4 times a day.

What if I take too much promethazine for sleep?

As with any other drug, taking too much promethazine can be quite troublesome.
In general, you shouldn't take more than 50 mg of promethazine. You could, but at that point, you're risking experiencing side effects and potentially overdosing.

If you do take too much promethazine hydrochloride to put yourself to sleep, you will most likely experience extreme sleepiness, along with breathing problems and heart palpitations. Arrhythmia and tachycardia are also quite common.

An image of a bottle of cough syrup.

In the case of an overdose, the symptoms could be various. They could include:

In case you do start experiencing any of the aforementioned symptoms, get to the doctor as quickly as possible, even though death is not a likely outcome.

So, all in all – promethazine for sleep will help you fall asleep, stay asleep, and it may even do something for your overall sleep quality. Just make sure you take a proper dose.

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About the author

Alex Petrović
Sleep Consultant
A CPD certified Sleep Consultant with more than 2000 hours of research into all the different ways we can get a great night's sleep. As a former insomniac, I know how difficult life can be without a nightly recovery and I love that I get to share everything I've learned with you all. So hopefully we can all sleep soundly!
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