While Benadryl (diphenhydramine) can safely be used once in a while as a sleep aid, long-term use is not recommended for multiple reasons.
Even the intermittent use of Benadryl for sleep isn't generally recommended if you are elderly (over 65).
Studies show that the elderly population doesn't metabolize Benadryl as quickly and are far more susceptible to the negative side effects of the drugs. For example, it can precipitate glaucoma, cause urinary retention and increase the risk of confusion in older adults.
The American Geriatrics Society 'Beers criteria', which discusses inappropriate medication use in the elderly, recommends against the use of Benadryl due to its strong anticholinergic effects (more on this later in the article).
OBRA (Omnibus Budget Reconciliation Act) guidelines, which has recommended policies on medication use in long-term care facilities, states that it should not be used for more than 14 days due to the risk of side effects and lack of published efficacy.
In terms of Benadryl possibility causing dementia, long-term use of anticholinergic drugs has been associated with an increased risk of dementia and dementia-related diseases, like Alzheimer's.
Benadryl is one of many anticholinergic medications that are thought to increase the risk of dementia, but studies show that this risk appears to be in those aged 65 years and older.
An anticholinergic drug is one that blocks the action of acetylcholine, an abundant neurotransmitter in the body.
Acetylcholine has a wide range of effects, which would be an article in and of itself. In a nutshell, it acts as a messenger in both the central and peripheral system and is vitally important to both memory and learning processes. It also activates motors neurons and is necessary for muscle contractility.
A drug having 'anticholinergic effects' isn't always a bad thing though.
In fact, there are several drugs specifically designed as anticholinergics, which are used for everything from an overactive bladder (e.g. Detrol LA) to the treatment of Parkinson's Disease (e.g. Cogentin, Artane).
Unfortunately, many other drugs have anticholinergic properties, which cause a range of undesirable side effects. These include:
- Dry mouth
- Dry eyes
- Increased body temperature
There are a variety of mnemonic sayings that describe 'anticholinergic toxicity' to help to remember the potential negative effects of anticholinergic drugs. One such one is:
"Blind as a bat, dry as a bone, full as a flask (can’t urinate), hot as a hare (or hell, or Hades), red as a beet, mad as a hatter, tacky (tachycardic) as a leisure suit (pink flamingo)".
Drugs often associated with their anticholinergic effects include:
- First-generation antihistamines (e.g. Benadryl)
- Tricyclic antidepressants
Anticholinergics are also fairly strongly associated with memory loss and an increased risk of dementia in those 65 years old and over.
Multiple studies warn against the long-term use of anticholinergics in the elderly due to this risk.
It isn't know how long anticholinergic drugs need to be taken to increase the risk of dementia, but one of the largest studies on the matter, published in JAMA Internal Medicine, reported a strong link between those taking high levels of anticholinergic medicines for more than three years and the onset of dementia.
The next section will focus on Benadryl.
Benadryl Anticholinergic Effects
First-generation antihistamines like Benadryl are strongly associated with anticholinergic effects.
These effects can be seen in many people taking the drug but the effects are far more pronounced in 65 years of age and older.
They are more likely to experience negative side effects in a more severe manner. These effects include:
- Memory loss
- Dry mouth
- Increased risk of falls
Benadryl, since it does have strong anticholinergic effects, is generally lumped into drugs that increase the risk of dementia with long term use in those over 65.
Benadryl As A Sleep Aid
Benadryl is widely used as a sleep aid due to its sedative properties.
In fact, several OTC (over the counter) sleep aid products (like ZzzQuil) contain only diphenhydramine (the active ingredient in Benadryl).
While Benadryl may be effective for short-term use to increase sleepiness in individuals, it doesn't appear to be overly effective in decreasing the time it takes to fall asleep (i.e. sleep latency) or in increasing the total time spent asleep. It also is associated with several negative effects, like a reduction in sleep quality and residual drowsiness (i.e. next-day sedation).
Long-Term Benadryl Use
Benadryl generally should not be used on a consistent basis long-term.
As mentioned previously, it also shouldn't be used (in most cases) in the elderly at all due to increased risk of side effects and its link with dementia.
As a general point though, Benadryl doesn't appear to be overly effective as a sleep aid, so long-term use may not provide much benefit anyway.
Several studies report that we become tolerant to the sedative effects of Benadryl quickly. Although it can cause sedation (or 'sleepiness') initially, this effect tends to significantly decrease after 4 days of continuous use.
Guidelines for the treatment of insomnia, provided by the American Academy of Sleep Medicine, don't even recommend the use of Benadryl at all for the treatment of insomnia:
Over-the-counter antihistamine or antihistamine/analgesic type drugs (OTC “sleep aids”) as well as herbal and nutritional substances (e.g., valerian and melatonin) are not recommended in the treatment of chronic insomnia due to the relative lack of efficacy and safety data.
Overall, while taking Benadryl once in a while to help you combat insomnia may work, long-term use likely won't be effective and only increase the risk of side effects.
More studies are needed to form a definitive conclusion in terms of the risk of dementia with long-term Benadryl use, but since we have a pretty good idea it may be unsafe in the elderly, it would be prudent to avoid it if you are over 65.
SummaryWhile it may work to help you fall asleep for a few days, long-term use of Benadryl as a sleep-aid likely isn't effective and is associated with several side effects like next-day drowsiness. Additionally, the long-term use of drugs like Benadryl in those 65 years old and over is linked with an increased risk of dementia.
- ^ Over-the-counter medications containing diphenhydramine and doxylamine used by older adults to improve sleep. PubMed
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