The People's Perspective on Medicine

Does Popular OTC Antihistamine Increase Risk of Dementia?

Why would anyone take a medicine that might increase the risk of dementia? We suspect that lots of people are unaware that many nighttime pain relievers contain diphenhydramine.
Surprised senior woman trying to close her alarm clock

The Food and Drug Administration has been surprisingly silent about the possible risk of dementia associated with anticholinergic drugs. It has been our observation that once this federal agency approves a medicine for OTC use it has a hard time warning about potential adverse reactions. That’s especially true if the danger is something as scary as the risk of dementia. This reader has a worrisome story to share:

Diphenhydramine (DPH) and Dementia?

Q. Both my mother and mother-in-law were diagnosed with Alzheimer’s. Mom was 76, and my mother-in-law was 72.

They lived very different lifestyles: Mom dealt with severe anxiety and depression, while my mother-in-law was a happy-go-lucky, active and vivacious health nut. The only common denominator they shared is that they both took diphenhydramine to sleep. Their doctors advised this!

Recently, an older friend at church said her doctor had advised her to do the same. I cautioned her against it.

Of course, our mothers might have developed Alzheimer’s regardless. I do believe diphenhydramine exacerbated the tendency. We must be our own health care advocates and watch out for our elderly loved ones as well.

Diphenhydramine (DPH) Is Found in Many Places:

A. Diphenhydramine (Benadryl) is an old-fashioned antihistamine that was originally developed to treat allergies. Because it often makes people drowsy, drug companies have added diphenhydramine to over-the-counter sleeping pills. Virtually all “PM” nighttime pain relievers contain this drug.

Diphenhydramine interferes with the action of the brain chemical acetylcholine. Long-term use of strong anticholinergic drugs has been linked to the risk of dementia (BMJ, April 25, 2018).  A review of sleep medicines in older adults concluded that:

“Diphenhydramine should be avoided in the elderly”(Clinical Therapeutics, Nov. 2016)

Doctors, DPH and Dementia:

It worries us that physicians are recommending DPH for insomnia. The authors who reviewed the “Safety and Efficacy of Sleep Medicines in Older Adults” wrote:

“Over-the-counter (OTC) or nonprescription medications such as antihistamines are frequently used for sleep. They are inexpensive and readily available options; however, they have limited data on safety and efficacy when used for insomnia. Diphenhydramine is the most commonly used OTC pharmacologic agent. OTC sleep aids should be utilized in short durations because tolerance can develop.”

What Does That Mean?

The authors go on to state:

“Furthermore, tolerance develops after 1 to 2 weeks of uninterrupted use of the antihistamines, which would render it an ineffective therapy.”

Geriatricians, writing in the American Journal of Medicine (June, 2006), note:

“Antihistaminics, such as diphenhydramine, may be used for their sedating effects. They are associated with cognitive impairment, daytime drowsiness, and anticholinergic effects. There are no specific data to show that antihistamines either improve insomnia or prolong sleep, and in general, these medications are avoided in the elderly because of potential side effects.”

There has been growing evidence that prolonged exposure to strong anticholinergic drugs has been associated with an increased risk of dementia.

Other Anticholinergic Drugs:

We suspect that many health professionals are unaware of the medications (both prescription and OTC) that have significant anticholinergic activity. Many are included in something called the Beers Criteria. These are medicines that should specifically be avoided by people over 65. The list was named after geriatrician, Mark Beers, MD. He was concerned that inappropriate drugs were being prescribed to older people far too frequently.

“According to the updated Beers criteria, diphenhydramine in particular should not be used as a sedative-hypnotic in the elderly.” (“Management of Chornic Insomnia in Elderly Persons” in The American Journal of Geriatric Pharmacotherapy, June, 2006).

In other words, older people (those over 65) should not use DPH as a sleeping pill. And yet the FDA has not been proactive in warning older people to stay away from PM pain relievers or other OTC drugs containing DPH. We find this disheartening.

We suspect that many of the purchasers of pain relievers containing diphenhydramine are are over 65. That would be especially true if their physicians recommend DPH for insomnia on the grounds that it is safer than prescription sleeping pills.

You can read other stories at this link:

Will Sleeping Pill with Diphenhydramine Lead to Memory Loss?

Where Can you Learn More?

We have written extensively about the hazards of medications for older adults in our book, Top Screwups. It is available in our bookstore at this link. To order by mail please send $15 plus $4 postage and handling to:

  • Graedons’ People’s Pharmacy, Dept. TSDM
  • PO Box 52027
  • Durham, NC 27717-2027.

Share your own story about DPH or other drugs that might increase the risk of dementia in the comment section below.

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    About the Author
    Joe Graedon is a pharmacologist who has dedicated his career to making drug information understandable to consumers. His best-selling book, The People’s Pharmacy, was published in 1976 and led to a syndicated newspaper column, syndicated public radio show and web site. In 2006, Long Island University awarded him an honorary doctorate as “one of the country's leading drug experts for the consumer.” .
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    The questions on Melatonin have not been answered. I started taking a 3 mg tablet at bedtime following information in an article from The People’s Pharmacy and do feel that I benefit from the drug. Please advise on the safety of continuing Melatonin.

    Thanks, Jane

    I am and have been concerned with the use of NSAIDs PM such as Advil , Excedrin etc. My concern has been with the use of them as pain relievers and I did not like to use them at all but particularly if I only use them to help me sleep. I have been taking a small drink, about 3oz of port wine at night and I find that that is very effective plus there is a minor benefit to red wine in addition to helping one sleep. Wine other than port does not appear to have the same benefit.

    Try magnesium as a sleep aid. It’s natural and very relaxing.

    In recent weeks I have been dealing with both seasonal allergies and frequent diarrhea. Aware of the problems with anti-cholinergic drugs, I was taking 25 mg of diphenhydramine hCl only when allergies were most bothersome, about every other night. Looking at my journal, I realized that I suffered from diarrhea only on the days when I had NOT taken the diphenhydramine the night before. I read that it is also used for motion sickness and can even cause constipation. I’ll be seeing my physician in a few days. Meanwhile, are there safer remedies for diarrhea?

    I am taking 3mg of Melatonin nightly and would like to know if it contains diphenhydramine. Is it safe to continue Melantonin on a daily basis?

    Thanks, Jane

    Jane, check the label. There should be information on what is in the pill.

    I have recently started taking betahistine dihydrochloride (8mg 3x a day)
    to help control symptoms of Meniere’s disease (vertigo, hearing loss, tinnitus). I wonder if this is an anticholinergic medication?

    What are your thoughts on using melatonin for sleep. It was suggested to me by a pharmacist. I use some small tablets that melt under the tongue.

    It’s always amazed and baffled me as to why some outrageously potent, and highly dangerous, prescription drugs are so quickly, easily,and automatically released into the OTC American supply chain. They are then freely sold to a vulnerable and mostly uninformed U.S. population to be easily purchased everywhere and anywhere, after the patents on these drugs have expired. Why? My only conclusion would be “influence peddling” in Washington DC by some very powerful and wealthy drug manufactures, and Wall Street Concerns.

    Antihistamines cross the blood brain barrier. It inhibits problem solving by causing drowsiness. I have found that they interact with many psychotropic medications.

    I have taken benedryl and zyrtec at night since year 2000 when I was dx with angioedema (tongue swells and I could die) from strong allergy to salicylates (aspirin and many other things). I am 81. I recently completed 2 books which are on Amazon. I don’t believe benadryl has caused me to lose brain power; it has prolonged my life, as I don’t suffer the anaphylaxis which was nearly fatal. I do my best to avoid any foods which might trigger it, of course.

    Everyone is different, and reactions to drugs vary.

    Such an effect as interfering with neurotransmitters should ring bells and whistles that diphenhydramine MUST be avoided by everyone, specifically those of us whose cognitive functions are showing diminished function. Lecithin would be useless as a supplement when taking an anticholinergic. There are other ways to treat insomnia. One suggestion which I was informed about years ago is that a glass of kool-aid before bed would be more efficacious then warm milk.

    * Be nice, and don't over share. View comment policy^