Why should older adults not take diphenhydramine? Understanding the risks

Oct 15, 2025 3 min read •

Geriatrics Senior Health Medication Safety

According to the American Geriatrics Society's Beers Criteria, oral diphenhydramine is considered a potentially inappropriate medication for adults 65 years and older. This guideline, based on extensive clinical evidence, highlights key reasons why older adults should not take diphenhydramine.

Quick Summary

Older adults are strongly advised to avoid diphenhydramine due to increased sensitivity to its side effects, which include a higher risk of cognitive decline, dementia, and accidental falls.

Key Points

Cognitive Impairment: Diphenhydramine blocks acetylcholine, a key neurotransmitter for memory, significantly increasing the risk of confusion and delirium in older adults.
Increased Fall Risk: The drug's sedative effects, dizziness, and impaired coordination heighten the danger of falls, which can lead to serious injuries like fractures.
Longer-Lasting Effects: Due to age-related changes in metabolism, diphenhydramine stays in the body longer, prolonging its negative effects and potentially causing daytime drowsiness.
Worsening Health Conditions: The medication can aggravate conditions common in seniors, such as enlarged prostate, glaucoma, and heart problems.
Ineffective Long-Term Solution: Tolerance to the sedative effects develops quickly, making diphenhydramine a poor and ultimately ineffective choice for treating chronic insomnia.
Safer Alternatives Exist: Modern, second-generation antihistamines (like cetirizine or loratadine) and behavioral therapies (like CBT-I) are safer and more effective options for managing allergies and sleep issues.

Despite its long-standing use as an over-the-counter remedy for allergies and sleep, diphenhydramine (commonly known by the brand name Benadryl) poses significant risks for older adults. These risks are exacerbated by the aging body's altered drug processing and diphenhydramine's anticholinergic effects. In older individuals, the drug's effects are more pronounced and last longer.

Increased Risk of Cognitive Impairment and Dementia

Diphenhydramine is a potent anticholinergic that blocks acetylcholine, a crucial neurotransmitter for memory. With age, natural acetylcholine levels decrease, making older adults more vulnerable to anticholinergic drugs.

Confusion and impaired thinking: Acute cognitive side effects like confusion and disorientation are common and can be mistaken for other conditions.
Potential link to dementia: Studies suggest a link between long-term anticholinergic use and increased risk of dementia, including Alzheimer's disease.

Heightened Risk of Falls and Accidents

Falls are a major concern for older adults, and diphenhydramine significantly increases this risk. Its sedative effects and prolonged presence in the elderly body impair balance and coordination.

Dizziness and grogginess: Lingering sedation can cause daytime drowsiness and dizziness.
Impaired coordination: Reduced reaction time increases the risk of accidents.
Bone fractures: Use of first-generation antihistamines has been associated with an increased risk of injurious falls or fractures in the elderly.

Exacerbation of Pre-existing Health Conditions

Diphenhydramine can worsen common health problems in older adults.

Urinary retention: Anticholinergic effects can make bladder emptying difficult, particularly for older men with an enlarged prostate.
Glaucoma: The drug can increase eye pressure, posing a risk for those with narrow-angle glaucoma.
Cardiovascular issues: It may cause rapid or irregular heartbeats, which is problematic for individuals with heart conditions or high blood pressure.
Breathing problems: Drying effects on mucus can be dangerous for those with asthma or other respiratory issues.

Reduced Efficacy and Development of Tolerance

Regular use of diphenhydramine for sleep can lead to tolerance, reducing its effectiveness. This often results in dose increases, further raising the risk of adverse effects. Non-pharmacological approaches like CBT-I are preferred for chronic insomnia.

Dangerous Drug-Drug Interactions

Using multiple medications is common in older adults, increasing the risk of interactions with diphenhydramine. It should be avoided with other central nervous system depressants, such as opioid pain relievers, benzodiazepines, other sedatives, alcohol, and other anticholinergic medications.

Comparing First-Generation (Diphenhydramine) vs. Second-Generation Antihistamines


Feature	First-Generation (Diphenhydramine)	Second-Generation (Loratadine, Cetirizine)
Mechanism	Easily crosses the blood-brain barrier, blocking histamine and acetylcholine.	Does not easily cross the blood-brain barrier, primarily blocking histamine in the periphery.
Side Effects (Older Adults)	High risk of sedation, cognitive impairment, confusion, falls, constipation, urinary retention.	Minimal risk of sedation or cognitive side effects.
Recommended Use (Seniors)	Strongly avoided by guidelines like the Beers Criteria.	Preferred option for allergies due to better safety profile.
Duration of Action	Relatively short-acting, but longer half-life in older adults leads to prolonged side effects.	Long-acting, providing 24-hour relief with less risk of residual effects.
Common Brands	Benadryl, Unisom, Tylenol PM, ZzzQuil.	Claritin, Zyrtec, Allegra.

Safer Alternatives for Older Adults

Second-generation antihistamines like loratadine or fexofenadine are recommended for allergies. For insomnia, safer alternatives include:

Good sleep hygiene: Consistent routines and a conducive sleep environment.
Melatonin: Short-term use may help, but consult a doctor.
Cognitive Behavioral Therapy for Insomnia (CBT-I): An effective non-medication treatment for chronic insomnia.

Conclusion: Prioritize Safer Alternatives for Senior Health

Medical experts advise against using first-generation antihistamines like diphenhydramine in older adults due to risks of cognitive decline, falls, and anticholinergic effects. Consult a healthcare provider for safe alternatives for allergies or sleep issues that suit your health needs. More information can be found in resources like the American Geriatrics Society Beers Criteria.

Frequently Asked Questions

Yes, Benadryl is a well-known brand name for the generic drug diphenhydramine. The same health risks for older adults apply to all products containing this active ingredient, including over-the-counter sleep aids.

Anticholinergic effects are a group of side effects caused by blocking the neurotransmitter acetylcholine. For older adults, this commonly manifests as confusion, blurred vision, dry mouth, constipation, and urinary retention.

As people age, their kidneys and liver may not clear medications as efficiently. This means diphenhydramine stays in the system longer, potentially reaching higher concentrations and extending its side effects.

For managing allergies, second-generation antihistamines like cetirizine (Zyrtec), loratadine (Claritin), or fexofenadine (Allegra) are safer alternatives because they have minimal anticholinergic effects.

Even occasional use carries risks, especially with pre-existing conditions like glaucoma or prostate issues. For occasional sleep trouble, behavioral strategies or a discussion with a doctor about safer options is recommended over using diphenhydramine.

Yes, many non-pharmacological methods are highly effective. These include practicing good sleep hygiene (consistent schedule, cool dark room) and therapies like Cognitive Behavioral Therapy for Insomnia (CBT-I).

While guidelines strongly advise against it, a doctor might approve its use for a short duration or for specific allergic reactions. It is important to confirm with your doctor why they recommend it and ensure they are aware of all your other medications and conditions.

References

Medical Disclaimer

This content is for informational purposes only and should not replace professional medical advice. Always consult a qualified healthcare provider regarding personal health decisions.