OTC Sleep Aids: A Risky Business

Many of us assume that over-the-counter drugs are safer than prescription drugs.

Yet the long-term effects of any drug can remain unknown for decades, and now researchers have found a correlation between long-term and/or high-dose use of OTC sleep aids and dementia.

Over-the-counter sleeping pills may not be as safe as we thinkSome insomniacs are leery of prescription sleeping pills but feel OK about sleep aids sold at the drugstore.

“I’m not really looking for medical intervention,” said Dale, a marketing manager who spoke to me about his insomnia as I was conducting interviews for my book. “I’m absolutely not interested in anything strong. But if it’s sold over the counter and I can take a half dose of it, that’s fine.”

Many of us assume that over-the-counter drugs are safer than prescription drugs. Yet the long-term effects of any drug can remain unknown for decades, and now researchers have found a correlation between long-term and/or high-dose use of OTC sleep aids and dementia.

Which Drugs Are Involved?

These drugs are called anticholinergics, among them the first-generation antihistamines that are now marketed as sleep aids. The active ingredient in these sleep aids is diphenhydramine or doxylamine. Here’s a list of common brand names:

  • Benadryl
  • Sominex
  • ZzzQuil
  • Tylenol PM
  • Excedrin PM
  • Nytol
  • Unisom
  • Store brands containing diphenhydramine and doxylamine.

Anticholinergic drugs block the action of acetylcholine, a neurotransmitter that plays an important role in waking us up and keeping us vigilant. When we’re awake, acetylcholine neurons are active in several areas of the brain. But the brains of people with Alzheimer’s disease show a marked reduction of acetylcholine and acetylcholine-secreting nerve cells. Other common anticholinergic medications include tricyclic antidepressants such as doxepin (Sinequan) and antimuscarinic drugs for bladder control such as oxybutynin (Ditropan).

Gist of the Study

Investigators at the University of Washington began tracking the medical records of 3,434 healthy 65-year-olds to see if anticholinergic medications increased their risk of developing dementia. About 23 percent of these older adults went on to develop dementia over a 7-year period.

Compared with people who did not take anticholinergic drugs, people taking at least 4 mg of diphenhydramine daily (1 capsule of Benadryl or ZzzQuil contains 25 mg of diphenhydramine), 10 mg of doxepin daily, and 5mg of oxybutynin for more than 3 years had a small increased risk of developing dementia. The risk increased in a linear fashion with higher doses and longer use.

Results in Perspective

This is not the first study to link dementia to the use of anticholinergic drugs. Researchers in Australia found that taking more anticholinergic medications was associated with greater risk of hospitalization for confusion or dementia. Researchers in Spain have concluded that long-term use of anticholinergic drugs “may generate a worsening of cognitive functions” and can also “initiate signs of dementia.”

None of the studies show that the relationship between anticholinergics and dementia is causal. Yet they do suggest that frequent use of OTC sleep aids may not be as harmless as many insomniacs suppose.

So what to do? Several prescription sleeping pills have also been connected to an increased risk of dementia, and a small body of research suggests that poor sleep may itself be a factor in the development of cognitive impairment. Now is the time to check into drug-free treatments for insomnia and be more sparing in the use of sleep meds, whether they’re handed over by a pharmacist or you can buy them right off the shelf.

 

The Low-Down on OTC Sleep Aids

Over-the-counter sleeping pills are readily available at the pharmacy: drugs like ZzzQuil, Benadryl, Unisom and Tylenol PM. All promise sound, refreshing sleep. Just how well do live up to that promise, and are they as harmless as they’re said to be?

OTC-sleep-aidOver-the-counter sleeping pills are readily available at the pharmacy: drugs like ZzzQuil, Benadryl, Unisom and Tylenol PM. All promise sound, refreshing sleep. Just how well do live up to that promise, and are they as harmless as they’re said to be?

These sleep aids work by blocking the secretion of histamine, a neurotransmitter that keeps you awake. Nearly every insomnia sufferer I know has tried them at some time or another, and some are satisfied customers.

“Whatever’s in Unisom, I’ve found it works for me pretty well,” says Dale, a marketing expert I interviewed for my book, whose main problem is getting to sleep at the beginning of the night and who sometimes wakes up in the middle of the night. “It’s 80 to 90 percent reliable.”

Other people with insomnia dismiss over-the-counter sleep aids as worthless. Existing scientific research suggests their efficacy is indeed fairly limited.

The active ingredient in most OTC sleeping pills is diphenhydramine (some formulations of Unisom contain doxylamine, a similar drug). In one study, diphenhydramine moderately increased subjects’ sleep efficiency (i.e., they spent more of their time in bed sleeping rather than lying awake).* In another study, older insomniacs taking the drug woke up a little less frequently at night.** Pretty small gains. Yet what behaves like a sugar pill for one insomniac can apparently work magic for another.

Downsides of OTC Sleep Aids

You might think, because these drugs are sold over the counter, that you can use them however you see fit without risk. Some are advertised as “non-habit-forming.” But here it’s better to be cautious. Studies suggest that if you take them every night, you’ll wind up needing to increase the dose to get the same sedative effect.

“Over-the-counter antihistamines may have a role for short-term insomnia treatment in younger adults,” write the authors of a review paper published last year, “but tolerance develops rapidly.”*** So nightly use of OTC sleep aids is not a good idea.

Lingering Effects

The other problem with these antihistamines is that their sedative effects are relatively long lasting and can cause morning drowsiness. Compared to newer prescription sleep meds, they have long elimination half-lives. (Half-life is the time it takes for a dose of a drug in the blood plasma to decrease by half.)

Diphenhydramine has a half-life of 2.4 to 9.3 hours, and its half-life tends to increase with users’ age. It will leave some people—older adults, especially—feeling groggy in the morning. The half-life of doxylamine is about 10 hours, and typically longer in older adults. It, too, may cause morning drowsiness, which increases the risk of falls and driving incidents.

Dale has found a way to cut down on the grogginess. “I use half the recommended dosage,” he says. “That minimizes the hangover in the morning.”

If you’re using OTC sleep aids, keep these caveats in mind.

*    Valerian-hops and Diphenhydramine

**  Temazepam and Diphenhydramine

*** Histamine-1 receptor antagonism