I took the Kirkland Signature sleep aid every night for the last week to see if it would help with both my insomnia and dust mite allergy.
The main active ingredient is the anti-histamine Doxylamine Succinate, which is also used in other brands of over the counter sleep aids. Kirkland Signature is a private brand of Costco, and their sleep aid is widely available in the United States.
Interestingly, it has identical ingredients to Unisom SleepTabs. Perhaps that’s why they felt the need to state on the label that it’s not made by the same company.
In this Kirkland sleep aid review, I’ll be describing my experience taking it, which should be similar to when I tried Unisom – in theory. And I’ll also cover some of the warnings and side effects.
The first night
My first impression was that the Kirkland sleep aid is, like Unisom, very small and easy to swallow.
The instructions tell you to take one tablet 30 minutes before going to bed. So I took one just as I got into bed and then read for a while. I always like to read after testing a sleep aid to see if there are obvious signs of sedation.
And since I was staying with a friend again, who has a notoriously dusty house (sorry if you’re reading this!), I wanted to see if it would stop my sniffling.
After around 30-40 minutes of reading, I did indeed feel that my nose was less irritated. And I also switched the light out to go to sleep.
I then woke up around 6.5 hours later, which is a good result for me. I often wake in the night at least a couple of times, and I average 6 to 7 hours’ sleep on a good night.
I felt a little groggy on first waking up, but it quickly cleared up after a shower and coffee. This was again very similar to the first time I took Unisom.
The following nights
As I was expecting, the pattern for the rest of the week when taking the Kirkland sleep aid was quite similar to the Unisom – though not exactly the same, just to be clear.
One thing is for sure, it definitely helped me in my eternal battle with the invisible hordes of dust mite.
As for sleep, I slept pretty well for 5 of the remaining 6 nights, though did have sporadic wakings. On the fifth night, I really didn’t feel any drowsiness and had a restless night. Maybe I slept well again the final night through tiredness – it’s impossible to say.
Increasing morning grogginess
The groggy next-day effect also increased throughout the week, as it did with all the anti-histamine sleep aids I’ve tried in the past. This seems inevitable if you continue taking them, which is why I rarely take them for more than a few nights at a time.
So by morning 4, it was taking a couple of hours to transition from what I’d put as 70% alertness on waking to 100% alert.
Still, it’s not a bad trade-off for what felt like a reasonably good night’s sleep, and distinctly better than the lack of alertness I feel after a night of endless tossing and turning.
So all in all, I felt like it did its job of helping me get off to sleep when I was having trouble sleeping in the previous days. And the side effects were tolerable, though I wouldn’t want to push it and keep taking the sleep aid for longer.
What evidence is there that the Kirkland sleep aid works?
As with most over the counter sleep aids, the manufacturer doesn’t need to conduct clinical trials to sell it. All they need to do is adhere to the general standards in the country where supplements and ingredients of this type are concerned.
So, it’s probably more useful to see what evidence there is that the active ingredient works as a sedative. And for that, there’s no shortage of medical sites that talk about it causing drowsiness. The FDA even approved Unisom for use as a sleep aid.
A team of researchers in 2012 pointed out that it’s been an established drug for more than 50 years:
Currently, doxylamine medicinal products have been authorized for more than 50 years, with an appropriate extent of use, for symptomatic treatment of occasional insomnia, making doxylamine a drug with a well established use.
However, a team of researchers in 2015, which examined previous research studies into over the counter sleep aids, had this to say:
Currently available literature suggests that commonly used OTC sleep agents, especially antihistamines and valerian, continue to lack robust clinical evidence supporting efficacy and safety in relevant populations
So perhaps there was a placebo effect at work when I’ve taken anti-histamine sleep aids. It might also help explain why some websites with many customer reviews have a mixture of people saying sleep aids like this one either work amazingly or do nothing.
According to the patient leaflet:
- There’s one active ingredient – Doxylamine Succinate, 25 mg
- Dibasic calcium phosphate
- FD&C blue no. 1 aluminum lake
- Magnesium stearate
- Microcrystalline cellulose
- Sodium starch glycolate
As I mentioned earlier, these are exactly the same ingredients as Unisom SleepTabs.
Who shouldn’t take this sleep aid
The carton has the following warnings:
1. Speak to a doctor before use if you have:
- A breathing problem, such as asthma, emphysema or chronic bronchitis
- Difficulty urinating because of an enlarged prostate gland
2. Ask a doctor or pharmacist if:
- You are taking any other medication
3. When using this sleep aid:
- Avoid alcohol
- Only take it at bedtime
4. Stop and speak to a doctor if:
- The sleep problem continues for two weeks
5. If pregnant or breastfeeding:
- Speak to a health professional first
6. Keep out of reach of children
7. If you overdose, get medical help or call a poison center
If you’d like to check this and more safety information, you can see the kirkland signature factsheet on drugs.com.
Warnings for older adults and children
I’ve seen an increasing number of medical sites recommend that older adults, as well as children, avoid Doxylamine Succinate. For example, WebMD says:
Older adults may be more sensitive to the side effects of this drug, especially drowsiness, dizziness, low blood pressure, confusion, constipation, or trouble urinating. Drowsiness, dizziness, and confusion can increase the risk of falling.
If you’d like some in-depth information about the use of this type of sleep aid among older adults, there’s an interesting research study from 2017 which looks into the issue and explains why it’s a potential problem.
Possible side effects
Like most over the counter sleep aids, the manufacturer is not required to list every possible side effect, since it’s sold as a supplement and not a prescription drug.
So, as with Unisom, I’ve checked medical sites like Mayo Clinic, WebMD and others for the known possible side effects of the active ingredient. They are:
- Dry mouth, nose or throat
- Constipation or difficulty urinating
- Stomach upset
- Memory problems
- Blurred vision
- Worse coordination
- Irregular or fast heartbeat
- Ringing in the ears
- Mental or mood changes (e.g. confusion, irritability, hallucinations)
- Easy bruising/bleeding
So is it safe to take?
Most drugs can cause side effects, often with scarily long lists of potential problems. But generally, Doxylamine Succinate is tolerated reasonably well by most people for short-term use.
Having said that, I do recommend talking it through with your doctor if you’re concerned. Try not to use it for more than a few nights, and if you have any side effects, stop taking it. Finally, also try to work on your sleep problems naturally.
Have you tried Kirkland Signature sleep aid? It’s always useful for readers to know what others think. So please feel free to share your experience in the comments below.