Insomnia? Anti-histamines should not be used!

We all know that sleep plays an extremely important role in ensuring our physical and mental health, allowing us to achieve maximum productivity. Unfortunately, insomnia is a problem that affects all of us at some point or other in our lives. It is by far the most common sleep complaint, with an estimate of 34% of adults having difficulty sleeping. Insomnia can be classified as transient (lasting only a few days), short term (lasting less than 4 weeks), or chronic (lasting more than 1 month). In most cases, insomnia occurs because of some other extenuating factor such as jet lag, pain or depression. If something else is preventing you from sleeping, you should always treat that condition or remove that barrier first before even considering sleep aids.

As the lack of sleep can be distressing and severely impact our day, it is common for some people to go to the pharmacy and purchase medicines to help them sleep. Some common medications bought over-the-counter for these purposes are sedative antihistamines such as diphenhydramine (Benadryl®), chlorpheniramine (Piriton®), and hydroxyzine (Atarax®). These medicines are actually used to treat allergies, but as some patients have found that these medications cause drowsiness, they are instead sought after as sleep aids. However, in reality this is not a healthy practice, and should not be recommended.

While it is true that sedative antihistamines make one drowsy, most people don’t realize that the sedative effect (which makes you calm and relaxed) may not necessarily translate to good sleep. These drugs may produce poor quality sleep with “hangover” effects that make you feel lethargic and drowsy the following day. Studies have also shown than tolerance to these drugs develop within 3-7 days, meaning that after a few days of use they become less effective in inducing drowsiness and sleep. In older people these drugs should be used with even more caution, as they can lead to cognitive impairment or even falls.

Even without the use of medicines, good sleep hygiene has been shown to help improve sleep, although many people find it hard to implement these techniques regularly and properly. Try these common practices if you have trouble sleeping. If you really need some medicine for your insomnia, talk to your doctor as there are better medicines that can be prescribed for this purpose.


Some Good Sleep Hygiene Practices
Maintain a regular sleep pattern. Get up and go to sleep at roughly the same time every day, even on the weekends.
Avoid stimulants. Caffeine, heavy meals, alcohol and nicotine should be avoided 4-6 hours before bedtime. While many believe alcohol is relaxing, it actually reduces the quality of sleep.
Establish a pre-bedtime ritual. Do the same relaxing activity every day just before sleep in order to condition your mind to a pre-sleep state.
Create the right environment. Ensure the bedroom is dark, quiet and comfortable to promote relaxation and avoid interruptions.
Turn the clock away. Face your clock away from your bed to minimize checking the time and reinforcing negative thoughts such as “I only have 4 hours of sleep left!’
Avoid naps. Avoid daytime naps to ensure you’re tired at bedtime. If you have to nap, keep it to less than 20 minutes to avoid disrupting your regular sleeping pattern.
Exercise regularly. Regular exercise promotes good sleep and should be encouraged, but ideally should not be done within 4 hours of bedtime.



(1)      Curry, D. T.; Eisenstein, R. D.; Walsh, J. K. Pharmacologic Management of Insomnia: Past, Present, and Future. Psychiatr. Clin. North Am. 2006, 29, 871–893.

(2)      Glass, J. R.; Sproule, B. a; Herrmann, N.; Busto, U. E. Effects of 2-Week Treatment with Temazepam and Diphenhydramine in Elderly Insomniacs: A Randomized, Placebo-Controlled Trial. J. Clin. Psychopharmacol. 2008, 28 (2), 182–188.




Jason Loo
Jason Loo

PhD, MPharm, RPh

As a computational chemist lecturing at the School of Pharmacy at Taylor's University Lakeside Campus.


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