Sominex Antihistamine Sleep Aid Review

sominex sleep aid

Sominex is an over the counter sleep aid that has the antihistamine promethazine hydrochloride as the active ingredient.

In this review, I’ll describe my personal experience of taking it, and the side effects I had. Please remember that this is just one person’s experience, and it might work differently for you.

Later in the article, you’ll also find important guidance and safety advice based on the patient leaflet and current medical advice.

The different types of Sominex

It’s important to first understand that there are several different versions of Sominex.

In the UK, the main ingredient is promethazine. However, in the US and Canada, it’s diphenhydramine. They are both antihistamines, but they aren’t the same.

Note that this review is based on the UK version only.

Secondly, don’t confuse it with the herbal sleep aid in the UK, which is completely different. For more about that one, you can see my Sominex Herbal review.

Finally, in India the name Sominex is used for a heartburn and indigestion drug, not as a sleep aid at all.

My experience

With the unbearable mugginess of a rare British heatwave turning my bedroom into a nighttime sauna, I’d had several bad nights’ sleep in a row.

I bought a pack of Sominex from Boots chemist while I was in the UK, where it’s available over the counter and online without a prescription. I took my first pill on a Sunday night, an hour before bedtime, in the hope it would put a stop to the sweaty sleeplessness.

I went to bed shortly after taking it to read a book, keen to keep an eye out for any noticeable sedative effect. After about 45 minutes, I remember starting to feel quite drowsy. I put my book down, turned off the light, and I’m pretty sure I was asleep in around 5 to 10 minutes.

A good night’s sleep

I only woke up once in the night, which was markedly different from the previous few nights. I remember feeling very out of it though, had a sip of water, and quickly fell asleep again.

I then woke up around eight hours later, which is unusual for me, even on the best of nights. I normally have at least two or three memorable wakings, so it seems the Sominex had done its job and knocked me out.

Morning grogginess

I definitely didn’t wake up feeling 100% alert. My head felt cloudy, very similar to when I took Nytol – another antihistamine sleep aid.

It wasn’t so bad though and after a strong coffee and a refreshing shower, I was probably at about 80% normal alertness.

That slightly groggy feeling slowly subsided over the next few hours, and by mid-morning, I was pretty much back to normal.

Testing again the following night

Another hot night and another Sominex pill to see how it would work two days in a row. Once again, I could feel the sedative effect creeping in just under an hour after taking it. I slept through the night with no wakings that I could recall.

I also realized that I normally get woken at least once by insanely noisy seagulls around 5 a.m.! So it was interesting that I slept even through their boisterous cacophony.

The fuzzy head appeared again though, and as with the previous day, it lasted into the mid-morning before losing the battle to strong coffee.

Would I recommend Sominex?

Sominex undoubtedly worked for me, and I don’t feel that it was just a placebo effect. I’ve had very similar experiences with other antihistamines, but not with herbal sleep aids.

Personally, I decided not to take it on the third night because I didn’t want any more morning grogginess. The temperature dropped a little anyway, which made it easier to sleep naturally.

I think it’s one to consider if herbal remedies aren’t quite potent enough for you – as long as you don’t mind a bit of a morning hangover.

Having said that, these antihistamines do have more safety warnings than herbal remedies. So check both the information below and the patient leaflet.

It’s also a good idea to consult your personal doctor before taking it, especially if you currently take any other medication. And if you’re an older adult, I recommend consulting your doctor before taking any antihistamine sleep aid.

Further information

sominex antihistamine sleep aid package

The following information is taken from the patient leaflet that came with the box of Sominex that I bought from a Boots chemist. Make sure you check yours if you buy it in case there are any changes to the guidance.

I updated this review on 29 March 2022 after checking the latest patient leaflet and the ingredients are the same as when I took it.

Sominex ingredients

  • Promethazine hydrochloride 20mg (the active ingredient).
  • Lactose.
  • Maize starch.
  • Croscarmellose sodium.
  • Magnesium stearate.


One tablet up to an hour before bedtime. If you take more than one, you should tell your doctor immediately or call emergency services.

How long can you take Sominex for?

It’s advised not to use Sominex for longer than seven days in a row. If you still don’t sleep normally after that, you should consult your doctor before taking more.

Who shouldn’t take Sominex

  • Children under 16.
  • Pregnant or breastfeeding women.
  • People trying to conceive – check with your doctor first.
  • If you’re allergic to promethazine or other ingredients.
  • If you’re allergic to Phenothiazine drugs. These are used for mental illness, nausea/vomiting or vertigo. Examples include chlorpromazine and pericyazine.
  • If you have concussion, lightheadedness, drowsiness, dizziness, or a recent head injury.
  • If you’ve taken MAOI drugs for depression in the last two weeks.
  • Don’t drink alcohol with it.
  • Don’t drive or operate machinery until the effects wear off.


You should consult your doctor before taking Sominex if you have:

  • Asthma.
  • Breathing problems or bronchitis.
  • Have experienced or are receiving treatment for seizures (e.g. epilepsy).
  • Difficulty passing urine.
  • Glaucoma.
  • Prostate, kidney or liver problems.
  • Heart problems.
  • Blocked intestine.
  • Lactose or sugars intolerance.

Interactions with other medicines

Check with your doctor before taking Sominex if you have recently taken, or plan on taking:

  • Any other medication that causes drowsiness (such as sedatives or relaxants).
  • MAOIs for depression.
  • Medicine that gives a dry mouth or blurred vision (e.g. atropine or anti-depressants).
  • Medicines used to prevent seizures.
  • Strong painkillers.
  • Medicines for mental illness.
  • Pregnancy tests based on urine samples (risk of false positive or negative result).
  • Allergy skin tests (don’t take Sominex in the three days before the test).

Possible Sominex side effects

Serious side effects

If you experience any of the following, you should stop using Sominex and contact a doctor immediately.

  • An allergic reaction resulting in trouble breathing, mouth or skin swelling, vomiting or stomach pains.
  • Jaundice.
  • Palpitations or abnormal heart rhythm.
  • Low blood pressure (feeling dizzy or lightheaded).
  • Blurred or poor vision, or eye pain.
  • Low energy or interest in doing normal activities.
  • Mouth ulcers, high temperature, bruising easily.
  • Convulsions.

Other possible side effects

Again, if you experience any of these, stop taking Sominex and speak to your doctor.

  • Drowsiness (outside of the time you are trying to sleep).
  • Confusion.
  • Dizziness or headaches.
  • Feeling clumsy or disorientated.
  • Shaking and trembling.
  • Stomach upset.
  • Dry mouth.
  • Difficulty peeing.
  • Feeling restless or excited.
  • Feeling or being sick.
  • Sensitive to sunlight.
  • Trouble sleeping.
  • Ringing noise in the ears.
  • Blocked or stuffy nose.
  • Rashes on the body.

Older adults warning

The patient leaflet also advises that older adults may be more susceptible to the side effects or confusion when taking Sominex. Again, if you’re an older adult (60-65+), it’s wise to consult your doctor before taking over the counter sleep aids.

To find out more about the possible side effects of Sominex, if you search for Sominex on the Boots website, there is a link to the current patient information leaflet at the bottom of the page under ‘attachments’.

Have you tried Sominex?

If you’ve taken Sominex, or are planning on trying it, it would be useful to hear from you. I know other readers always appreciate seeing a variety of experiences beyond mine.


    • Hi Dennis
      I’m not sure to be honest. I saw one post on Reddit from a pharmacist saying it was a supply issue, but I can’t confirm that. I just took a quick look, and it seems you can still get it online, but not in stores currently.

  1. Hi!
    I work a lot of nights, and when I come off of nights and have a week off, I need to get my body clock back to normal. So, I tried Sominex and took one the first night so I would sleep through. It definitely works, but it does leave you groggy and feeling tired in the morning. I got 13 hours of sleep altogether and couldn’t sleep the following night. So, I cut one in half, and it was better. But for me, I now cut one tablet into quarters, and I just take a quarter. It sends me to sleep, but I wake up at 7 or 8 am and don’t feel drowsy. And you get more for your money. It’s a win-win for me.

    • Hi Val
      Thanks for sharing your experience. It sounds like it’s working well for you. I also sometimes take smaller doses than recommended, especially when trying a new sleep aid if I find the initial dose leaves me feeling groggy.

  2. Dear Mr. Green,
    Thank you for your review of Sominex– I live in the States so diphenadrine is the active ingredient like you stated.
    I’m a 60 y/o female and have been suffering from insomnia quite a bit lately to the point that it interrupts my husband’s sleep. I didn’t have any sleep aids so I used the Tylenol PM that I had in the medicine chest. That worked fine since it has the same ingredient as sominex but I don’t want to have to depend on diphenadrine nightly so I better do more physical work/exercise during the day to tire my body. I find that listening to Enigma or Patrick O’Hearn is relaxing in the evening.

    • Hi Sheila
      You’re welcome, I hope it was helpful! I definitely think doing exercise and some form of work during the day is one of the keys to a better night’s sleep. It may not be enough for some people, depending on what is behind the sleep problems, but as a rule of thumb, it certainly makes a difference for me!

  3. I tried this for the first time this week. I can get to sleep but can’t stay asleep. I had considered taking one when I woke during the night but followed the instructions.
    One of my reasons for trying this is menopausal itching during the night which wakes me too.
    On taking it before bed I found it relaxed my body but didn’t help with itching or keeping me asleep all night. Would a few nights taking this regularly work or should it work the first time? I’ve always just taken pain relief to try to sleep.
    Thanks for sharing your experience.

    • Hi Joanne
      I think they are supposed to work on the first night – if they are going to work. I’d ask your doctor to see if they think it’s a good answer to the sleep and itching problems combined.

  4. I’ve been taking half a tablet of Sominex for years on and off as I suffer from such bad insomnia! Think I’ve taken it so long now I’m immune to it, so it has no effect, but still take them hoping for a good night’s sleep! It’s a vicious circle.

    • Hi Caroline
      Thanks for sharing your experience. That’s a long time to be taking an antihistamine sleep aid! How regularly do you take them, when you say on and off? If they aren’t working for you any more, perhaps you’ll have more success with trying natural techniques? Have a look at my main page about sleep habits for some ideas that you may or may not have already tried.

  5. I’ve had insomnia for years, my doctor doesn’t want to prescribe me anything so I take these (half) frequently, any issues with taking them long-term?
    I don’t generally have a problem going to sleep it’s the waking at 2 or 3am and can’t get back off,

    • Hi Chris
      Sorry to hear you’ve had insomnia for so long. I don’t think it’s generally advised to take antihistamines long term as a solution for insomnia. I don’t know how old you are, but if you are an older adult (60/65+) then it’s worth investigating antihistamines for sleep too as they are not always advisable for older adults due to the increased risk of adverse side effects.

  6. I’ve struggled with bouts of sleeplessness for 25 years. I’m a fit and healthy 45 year old bloke. Doctors are really reluctant to prescribe anything except eating well and getting into a routine, however the latter isn’t always an option!
    I’m trying my first Sominex Promethazine this evening, fingers crossed!
    Will update with results tomorrow, although a little concerned about my gym appointment at 8am…

    • Hi
      It worked really well actually, I got to sleep more quickly and although I still stirred a few times, I managed to get back to sleep each time.
      Not too groggy in the morning either.
      Will use again

    • Hello. I tried Nytol non-herbal and felt really anxious and panicky. It was probably one of the worst nights ever! Are these the same ingredient or a similar one? I’m a bit worried about trying them in case I have the same reaction. Thanks.

      • Hi Rosie
        Sorry to hear you had such a horrible experience. The ingredients are different, but they are both antihistamines. I would avoid any similar ones until you have a chance to talk to your doctor to see what they say about your reaction to the Nytol.

  7. Hi,
    After a very traumatic experience that lasted several months, I had difficulty with sleep for 4 years working on little sleep which left me exhausted. I have been using Sominex 1/2 tab for the last few weeks and have had good sleep 7 -8 hours. I understand it is not suggested to use for long periods, however, the lack of sleep for so long also must have been extremely bad for my health. I experience a little sluggishness until coffee then fine. I will try to reduce and wean off but value the sleep after so long.

    • Hi Carol
      Thanks for sharing your experience. I understand the desire to stick with the good sleep even knowing the advice not to use sleep aids for long periods. I’d suggest keeping a close eye out for other side effects though. In my experience, they tend to get worse over time with antihistamines.

      • It’s the devil and deep blue sea. No sleep or sleep with potential side effects! I am not a fan of any drugs and as a retired Nurse, Operating Department Practitioner I am fully aware all drugs have side effects. I personally came to a breaking point after trying all other non-drug methods to aid sleep. I exercise over 10 hours per week and have a fairly good balanced diet. I will continue to try and wean off completely moving on. Thanks for your response Ethan appreciate the feedback.

        • No problem. Love that idiom by the way, and it’s a fitting one for the age-old question of sleep problems.
          Good luck in your journey, and I hope you get to the point of natural sleep you’d like.

  8. Hello, I have suffered from insomnia for a couple of years now and have been under the doctor off/on over that time. I found that Zopiclone or Zolpidem were the only things that worked for me but were only ever short term due to dependency risk (other things like Temazepam and Amitriptyline did not work). My doctor recently prescribed Sominex and I was somewhat sceptical of it’s ability to work for me given that it was an OTC however I have found that it’s been really effective in helping me to drop off quickly and to stay asleep longer.

    • Hi Simon I also had not slept for years sometimes dropping off around 5 am. Doctors wouldn’t help, then I saw Sominex on a Website and have now been on them for months and how wonderful a good night’s sleep is.

  9. Hi. My sleep disappeared one night 2.5 years back and zopiclone 3.75mg ( one each night ) helped immediately and continued to help. Sadly the GP’s are cutting down and telling me to stop, which would be terrible with less than 2 hours a night in chronic pain with fibromyalgia. My friend told me about these today. I am grateful if they help me when I try them. My friend said she switched to them when her zopiclone was suddenly stopped after 6 years and they are helping her. I wrote this review before trying them. I will update after. Primarily, I wrote this for zopiclone users suddenly told their working medication will be stopped, to help them find this on an internet search and provide them the name of a medication that may help them, as it helped another zopiclone user, who described the night’s sleep as the same on both medications. I hope this helps me too.

    • Hi Ruth
      Thanks for sharing your experience. I hope they help you – do let me know if you have any updates!

  10. I was diagnosed with tinnitus in Jan 2016 and was started on promethazine to help me sleep.

    To be honest, promethazine gave me my life and normal routine back. I’ve been on a 75mg dose for just over three years, but sadly it seems in the last two weeks I’ve become tolerant to it.

    My sleep has been inconsistent, some days it’s 4-5am before I finally switch off. My GP gave me 7xZopiclone 3.75mg last week but I’m hesitant to take them to due to the risk of side effects and dependence.

    I honestly feel like I’m at a dead-end at age of 24.

    Anyway, this blog has been extremely useful. Thanks Ethan.

    • Hi Andy
      Is tinnitus the principle reason you can’t sleep, or is there something else going on for you?

    • Hey Andy.

      I’ve been suffering from insomnia (due to clinical depression/anxiety) since 2013 now and I tried all the off the shelf things before I went to the doctors who at first gave me Trazodone (it’s an antidepressant idk if you’ve heard of it) but maybe try that?

      It didn’t work for me but I’ve heard it works for some people, after a suicide attempt in 2015 I saw a Psychiatrist and they prescribed me with a continuous script of Zopiclone (when my Dr had previously prescribed this it was only 7 at a time and you couldn’t go back and request more for a few months) these didn’t work for me so they switched me to another Z-drug which is Zolpidem (Ambien) which I have taken every night ever since. It works for me but I am also dependant on it now I guess so I understand your feelings on that.

      Also, I am prescribed the anti-psychotic Promazine, for my anxiety, this is a relative of Promethazine and definitely knocks me out more than any other medication ever has, but anti psychotics have some quite unwanted side effects over the long term, but idk I’m just saying what’s worked for me.

      I hope you can resolve your insomnia. Take care.

  11. I’ve been using Sominex occasionally for a few years and have found it to be the best over the counter sleep aid for me personally. My usual sleep is awful, getting a few hours at the start of the night and then remaining awake from about 2 or 3 onwards, but these see me through till 6am or later, usually unbroken.
    I’ve slowly had to up my dose from 1/2 tablet through to now taking a whole tablet, but don’t get the hangover effect quite so much these days despite increasing the dose.
    I wouldn’t recommend with any alcohol at all as it renders them useless in my experience.

    • Hi Andy
      Thanks for sharing your experience. It sounds similar to mine nowadays where a tolerance builds quickly with antihistamines. And I agree that mixing alcohol with these, or any other sleep aid, is generally not a good idea.

  12. Got these from my pharmacist as a stand in for the Zolpidem my Dr provides as have sleep problems with A/F medication amiodarone and Bisoprolol. Could not believe how good they were as slept right through from midnight to 6am. Tried Boots Sleepease with Something beginning with D as main ingredient but it gave me restless legs. My legs are better and I slept like a baby.

    • Hi Mike
      Thanks for sharing your experience. It seems like they worked really well for you!

  13. This is a personal experience and would most likely work differently for everybody else. I’ve taken Sominex on three occasions and every time I take it, I feel sick, I develop an infection my immune system would normally fight against. I feel the drug sedates the entire body in such away that the whole body system goes to sleep except the brain. I advise the drug is taken in smaller doses I.e 1/2 or 1/4, or not used at all.

    • Hi Ope
      It sounds like it’s not right for you at all. As you say, everyone is different. But if I had those reactions, I would personally avoid it.

  14. Hi Ethan,
    Just took my first Sominex about 15 minutes ago. It’s only 9.15 and it’s Valentines Day so maybe a little early! I can feel the drowsy effect kicking in already.
    Looking forward to a nice long sleep!
    Best wishes,

  15. I tried Sominex last night. OMG!!!! I hadn’t slept this well since I was a baby. Uninterrupted sleep for 9 hours!!! I had no side effects upon awakening.

  16. I find that a quarter of a tablet is enough – I still feel a little groggy until I have had my morning cup of tea, so I can’t imagine how I would feel if I took a whole tablet. I only use it when I have had a run of bad nights, because I am concerned about becoming addicted even though it seems to suggest that it doesn’t cause addiction – but of course there can be psychological addiction as well as purely physical.

  17. Hi just wondering if somminex works. I take zopiclone occasionally but am reluctant to take them all the time and I only get 14 to last me the month because it can get addictive so want to try something else, any advice please.

    • Hi Rachel
      Personally, I wouldn’t start filling gaps with another sleep aid without my doctor’s guidance. And taking anti-histamines like this on an ongoing basis isn’t usually advised either. I would talk this through with your doctor and explain how the supply is affecting you.

  18. Hello Ethan

    I take a half tablet periodically to get myself off to sleep when I’m struggling and it works a treat for a deep sleep. I’m sure the magnesium in it helps with menopausal magnesium deficiency too. Grogginess is minimal.

    • Hi Sue
      Thanks for your comment. I’m not sure about the magnesium, but as long as it helps you, that’s the main thing!

  19. Hey Ethan.
    I take two of these when needed and get about 5 hours sleep before I wake, usually my insomnia is so bad I wake every hour if I don’t take anything which gets more annoying than anything. It’s just the next day grogginess with Sominex that is a pain but a strong coffee or two and I feel more alert. People who sleep well every night don’t realise how important sleep is for our physical and mental health when they take it for granted. Not in enough sleep and I pace the house and feel like I’m going crazy. Doctors are mostly unsympathetic (maybe because they sleep well!). Maybe one day I’ll sleep like a normal person. Harry.

    • Hi Harry
      Thanks for your comment. I agree that a couple of coffees is sometimes needed to break through the grogginess. It’s probably not a good thing though, especially in the long run.
      I imagine doctors do understand what a lack of sleep feels like – they were all students, interns or junior doctors at some point working crazy hours and sleeping where and when they could!

  20. I’ve been taking it for about two weeks and it’s given the best night’s sleep I’ve had for years. Grogginess the next day can be a problem I’ve noticed, especially if I take too late at night. So far so very good all the same.

    • Hi Calum
      Thanks for your comment. I know what you mean! I think it’s a common issue with sleep aids, especially anti-histamines in my experience. They can work very well, but you do need to weigh up the pros with the cons of the next day hangover effect.
      I find it sometimes has an accumulative effect, so watch out for that. The grogginess can be tolerable for a few days, or even couple of weeks. But sooner or later, it always gets a bit much. Then only when you stop taking them, so you realise just how groggy it had been making you!

    • Hi Liz
      Thanks for sharing your experience with Sominex. It’s useful to hear other people’s views!

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