9 Common Over-the-Counter Pills That May Affect Memory and Thinking

Have you ever walked into a room and suddenly forgotten why you went there?

Maybe you misplaced your keys.

Maybe you read the same sentence twice.

Maybe someone's name was sitting on the tip of your tongue—but disappeared before you could say it.

These moments can be frightening.

And when they happen repeatedly, it is natural to wonder:

"Is this simply aging—or could something I'm taking be affecting my brain?"

That question deserves more attention than it usually gets.

We often think of over-the-counter medicines as harmless because we can buy them without a prescription. But OTC does not mean risk-free. Some medicines can cause drowsiness, confusion, impaired attention, or other cognitive effects, particularly in older adults.

The National Institute on Aging specifically recommends reviewing prescription medicines, OTC medicines, and supplements when evaluating cognitive problems. It highlights medications with anticholinergic properties and certain antihistamines as medications worth reassessing.

But there is an important distinction:

A medication being associated with cognitive problems does not automatically mean that it causes permanent memory loss or Alzheimer's disease.

Some effects are temporary. Some evidence comes from observational studies. Some medicines have stronger evidence than others.

So rather than creating fear, let's look at the evidence carefully.

Why Can Some Medicines Affect the Brain?

One important mechanism involves something called anticholinergic activity.

Acetylcholine is a neurotransmitter involved in attention, learning, memory, and other brain functions.

Some medications block acetylcholine's effects. These medications can be useful for treating allergies, motion sickness, insomnia, and other problems—but their effects can also include sleepiness, confusion, impaired attention, and cognitive difficulties.

Research has found associations between higher anticholinergic exposure and cognitive decline or dementia, although observational studies cannot prove that the medicines themselves directly cause dementia.

This matters particularly as we get older.

1. Diphenhydramine

Commonly found in: allergy medicines and nighttime sleep products.

Diphenhydramine is probably one of the most important OTC ingredients to know about.

It is a first-generation antihistamine with strong anticholinergic effects. It can cross into the brain and cause significant drowsiness.

The problem isn't necessarily taking one occasional dose exactly as directed.

The bigger concern is frequent or repeated use, particularly among older adults.

Studies have associated diphenhydramine with cognitive impairment and delirium in older patients.

Current MedlinePlus information also warns that diphenhydramine generally should not be used in adults 65 and older except for certain serious allergic reactions unless a healthcare professional recommends it.

Look for it on labels as:

Diphenhydramine HCl

You may encounter it in products marketed for:

• allergies
• nighttime relief
• sleep
• colds
• coughs

Important: Never assume that a product is different simply because the brand name is different. Check the active ingredients.

2. Doxylamine

Commonly found in: OTC nighttime sleep aids and some nighttime cold products.

Doxylamine is another first-generation antihistamine.

It can make you extremely sleepy, but its effects aren't limited to sleepiness. Because of its anticholinergic activity, it can contribute to confusion and impaired mental function, particularly in older adults.

The FDA has specifically noted that diphenhydramine and doxylamine are used for occasional sleeplessness and that their anticholinergic effects can increase the risk of confusion and delirium in older adults.

MedlinePlus also advises people 65 and older to discuss the risks and benefits of doxylamine with their doctor because older adults generally should not use it unless specifically advised.

The bigger question isn't:

"Did this pill cause Alzheimer's?"

The better question is:

"Could this medicine be contributing to the brain fog or confusion I'm experiencing?"

That's a conversation worth having with a healthcare professional.

3. Chlorpheniramine

Chlorpheniramine is another older-generation antihistamine found in some OTC allergy and cold medicines.

Like other first-generation antihistamines, it has anticholinergic properties and can cause:

• drowsiness
• slowed reactions
• confusion
• difficulty concentrating
• impaired alertness

MedlinePlus specifically advises older adults to discuss the risks and benefits of chlorpheniramine because it is generally not as safe or effective for this age group as some alternatives.

The tricky part is that people don't always realize they're taking it.

A combination cold or allergy product may contain several active ingredients.

That's why reading the Drug Facts label matters.

4. Brompheniramine

Brompheniramine belongs to the same general family of older antihistamines.

It can appear in combination cold and allergy products, which makes it especially important to look at the active ingredients rather than simply the product name.

First-generation antihistamines as a group have attracted attention because of their anticholinergic effects.

Recent observational research involving hundreds of thousands of people with allergic rhinitis found an association between cumulative antihistamine exposure and dementia risk, with stronger associations at higher cumulative exposure. However, the researchers also emphasized that additional clinical trials are needed to establish causation.

That distinction is critical.

Association is not proof that an antihistamine causes dementia.

But if you regularly use an older antihistamine, especially as you age, it may be worth asking whether a different treatment would be more appropriate.

5. Dimenhydrinate

Commonly used for: motion sickness and nausea.

Dimenhydrinate is another OTC antihistamine with anticholinergic properties.

It can cause substantial drowsiness and impaired alertness.

MedlinePlus advises people 65 and older to discuss the risks and benefits because older adults generally should not use dimenhydrinate unless recommended.

There are also published reports describing cognitive impairment associated with chronic high-dose use. A 2024 case report involved long-term high-dose dimenhydrinate misuse, so it should not be interpreted as evidence that ordinary occasional use causes permanent cognitive impairment.

That difference matters.

Occasional, correctly used medication is not the same thing as chronic high-dose misuse.

6. Meclizine

Meclizine is commonly used for motion sickness and dizziness.

It is another medication with anticholinergic effects.

For some people, the immediate problem isn't "memory loss" but something subtler:

You feel mentally slower.

You may feel sleepy, less alert, or have difficulty concentrating.

MedlinePlus specifically recommends discussing the risks and benefits of meclizine with a doctor if you're 65 or older because older adults generally should not use it routinely.

If you're regularly using meclizine and noticing new brain fog, don't simply assume you're "getting old."

Ask whether the medication could be contributing.

7. Cimetidine

Cimetidine is an OTC acid-reducing medicine in the United States.

Unlike the antihistamines discussed above, its cognitive concern is different.

There have been reports of confusion and central nervous system effects, particularly in vulnerable older adults and people with impaired kidney or liver function.

This doesn't mean ordinary cimetidine use causes dementia.

Instead, it illustrates something important:

A medication can occasionally affect mental clarity without causing a neurodegenerative disease.

If someone suddenly becomes confused after starting a medication, that deserves medical attention rather than being dismissed as normal aging.

8. Famotidine

Famotidine is another acid-reducing medication that is available OTC.

Reports have described mental confusion associated with H2-blocking medications, especially in older patients with kidney problems.

Again, this is not evidence that famotidine causes Alzheimer's disease.

The concern is more about medication-related confusion or cognitive symptoms in susceptible individuals.

If you're older, have reduced kidney function, take multiple medications, and suddenly notice unusual confusion, your entire medication list should be reviewed.

9. Omeprazole and Other OTC Proton Pump Inhibitors

This category requires the most caution because the internet has often exaggerated the evidence.

OTC proton pump inhibitors (PPIs) include medicines such as omeprazole and lansoprazole.

Some observational studies have reported associations between PPI use and dementia, while other studies have found no meaningful association.

A systematic review and meta-analysis found no clear evidence that PPI use increases dementia risk.

An even newer 2026 umbrella review concluded that most systematic reviews and meta-analyses do not support a convincing causal relationship and described the overall certainty of the evidence as low.

So should you stop taking your PPI because you're afraid of Alzheimer's?

No.

If you have a legitimate reason to take it, don't stop it based on an internet article.

Instead, ask your doctor or pharmacist:

"Do I still need this medication, and is this the right dose and duration for me?"

That's a much safer approach.

The Bigger Issue: Your Total Anticholinergic Load

Here's something many people don't realize.

You might not take one obviously "strong" medication.

Instead, you might take several medications that each have modest anticholinergic effects.

For example:

• an allergy pill
• a nighttime cold medicine
• a sleep aid
• a motion-sickness medication
• another medication prescribed for a different condition

Individually, each one may seem insignificant.

Together, the effects can add up.

Research has found that increasing cumulative exposure to anticholinergic medications is associated with higher dementia risk in observational studies.

This is one reason medication reviews become increasingly important with age.

Does Taking These Medicines Mean You Will Get Dementia?

Absolutely not.

This is probably the most important message in this entire article.

Researchers have found associations between certain medications—especially medications with anticholinergic properties—and cognitive problems or dementia.

But observational research cannot always determine whether:

the medication caused the problem,

or whether

the health condition requiring the medication, other illnesses, age, lifestyle, or other factors contributed to the problem.

For example, people who regularly have allergies, insomnia, dizziness, chronic pain, or other health problems may already have different health characteristics from people who don't use those medications.

That's why we should not turn an association into a frightening guarantee.

Temporary Brain Fog vs. Long-Term Cognitive Decline

There is also a huge difference between:

Temporary medication effects

Such as:

• sleepiness
• confusion
• difficulty concentrating
• slower reaction time
• feeling "foggy"
• trouble remembering something while sedated

and:

Long-term cognitive decline

Such as:

• progressively worsening memory
• difficulty managing familiar tasks
• repeatedly getting lost
• significant personality changes
• increasing difficulty communicating
• problems with judgment

One does not automatically mean the other.

In some situations, medication-related cognitive symptoms may improve after the medication is changed or discontinued under professional supervision.

Why Older Adults Need Extra Caution

As we age, our bodies can process medications differently.

Kidney function, liver function, body composition, sensitivity to sedating drugs, and the number of medications being taken can all change.

And many older adults take multiple medications simultaneously.

The National Institute on Aging warns that polypharmacy can increase the possibility of side effects and unintended problems and recommends discussing whether medications can safely be reduced or stopped when appropriate.

This is not about blaming medication.

Medication saves lives.

The goal is to make sure every medicine has a reason to be there.

7 Questions to Ask Your Doctor or Pharmacist

If you're worried about memory or brain fog, take your medication list with you and ask:

1. "Could any of my medicines affect my memory or concentration?"

2. "Am I taking an anticholinergic medication?"

3. "Could two or more of my medicines be causing similar side effects?"

4. "Do I still need every OTC medicine I take?"

5. "Is there a safer alternative for someone my age?"

6. "Could my dose or duration be reduced?"

7. "Could another health problem be causing my memory symptoms?"

These questions can lead to a much more useful conversation than simply asking:

"Which pill causes dementia?"

Don't Make This Mistake

If you recognize one of these medications in your medicine cabinet, don't suddenly throw it away.

Some medicines should not be stopped abruptly.

And some are necessary for managing important health conditions.

Instead:

Write down the medication → write down the dose → write down how often you take it → bring the list to your doctor or pharmacist.

The NIA recommends keeping a complete list of prescription medicines, OTC medicines, vitamins, and supplements and sharing that information with healthcare professionals.

And Don't Forget the Combination-Medicine Trap

One of the easiest ways to accidentally double up is through combination products.

You might take one medicine for allergies and another for a cold.

Both may contain the same antihistamine.

Or you might take a nighttime product containing an antihistamine and then take another sleep product containing another sedating ingredient.

That's why reading the Active Ingredients section of the Drug Facts label is so important.

Don't judge a medicine by the front of the package.

Read what's inside.

When Memory Problems Should Be Checked

Everyone forgets things sometimes.

But persistent or worsening memory problems deserve attention.

The National Institute on Aging recommends discussing ongoing memory problems with a healthcare professional because identifying the underlying cause can help determine appropriate treatment.

Seek prompt medical attention for sudden confusion, a sudden major change in mental status, difficulty speaking, weakness, facial drooping, severe headache, or other sudden neurological symptoms.

Those symptoms can indicate an emergency and should not simply be blamed on medication or aging.

The Gentle Truth About Memory

Perhaps the hardest part about memory problems isn't forgetting a name.

It's the fear behind the forgetting.

"What if this gets worse?"

"What if I'm losing myself?"

"What if my family notices?"

Those thoughts can hurt.

But a forgotten name doesn't automatically mean dementia.

And taking an OTC medicine doesn't automatically mean you've damaged your brain.

Sometimes the answer is surprisingly practical: review the medication list, check for interactions, examine sleep and other health factors, and talk with a qualified professional.

Your brain deserves investigation—not panic.

Your memory deserves attention—not fear.

And if a medication is contributing to the problem, discovering that possibility can be an empowering first step.

Learn More:

1. Can the Brain Feel Pain? The Mind-Blowing Anatomy Behind Your Worst Headaches
2. NeuroPrime Review 2026: Ingredients, Benefits, How It Works, Price & Is NeuroPrime Worth Trying?
3. Is Your Brain Working Harder Just to Hear? The Silent Link to Memory Decline

Quick Takeaway: The 9 OTC Medicines to Know

OTC medicine/ingredient	Main concern	Evidence level
Diphenhydramine	Anticholinergic effects, sedation, confusion	Stronger concern
Doxylamine	Anticholinergic effects, confusion	Stronger concern
Chlorpheniramine	Anticholinergic effects, sedation	Concern, especially in older adults
Brompheniramine	First-generation antihistamine effects	Concern with cumulative exposure
Dimenhydrinate	Sedation and anticholinergic effects	Concern, especially repeated/high-dose use
Meclizine	Sedation and anticholinergic effects	Concern in older adults
Cimetidine	Possible confusion/CNS effects	Less common; susceptible people
Famotidine	Rare mental confusion reported	Uncommon/conditional concern
Omeprazole/other PPIs	Dementia association has been investigated	Evidence remains inconsistent

The evidence is not equally strong for all nine. The strongest and most consistent concern in this list involves medications with significant anticholinergic effects. The evidence surrounding PPIs and dementia, for example, remains inconsistent and does not justify stopping an indicated medication.

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Sometimes protecting your memory isn't about buying another "brain supplement."

It may begin with something much simpler:

Look at what you're already taking.

Read the labels.

Ask questions.

Review your medicines.

And don't be embarrassed to say:

"I've noticed changes in my memory. Could any of my medications be contributing?"

That single question could lead to an important conversation about your health.

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Health Disclaimer

This article is for educational and informational purposes only and is not medical advice, diagnosis, or treatment. It is not intended to replace advice from a qualified physician, pharmacist, or other licensed healthcare professional.

Do not stop, reduce, or change a prescription or OTC medication because of this article without discussing it with an appropriate healthcare professional. Some medications may need to be tapered or otherwise managed carefully.

The relationship between medications and memory or dementia is complex. Some studies show associations, but an association does not necessarily prove that a medication causes dementia. Individual risk can vary according to age, medical conditions, kidney and liver function, dose, duration of use, and other medications.

If you experience sudden confusion, sudden memory loss, trouble speaking, weakness, severe headache, loss of consciousness, or other sudden neurological symptoms, seek emergency medical care.

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Reliable Sources & Further Reading

• National Institute on Aging — Taking Medicines Safely as You Age — practical guidance on OTC medicines, medication lists, interactions, and medication reviews.
• National Institute on Aging — Caring for Older Patients With Cognitive Impairment — discusses reviewing OTC and prescription medications that may contribute to cognitive problems.
• PubMed — Anticholinergic Drugs and the Risk of Dementia: Systematic Review and Meta-analysis — review of evidence involving more than 1.5 million participants.
• PubMed — Anticholinergic Drug Exposure and Dementia Risk — large observational study examining cumulative anticholinergic exposure.
• MedlinePlus — Diphenhydramine — drug information and older-adult precautions.
• MedlinePlus — Doxylamine — drug information and precautions for adults 65+.
• PubMed — PPI Use and Dementia: Systematic Review and Meta-analysis — evidence finding no clear association between PPI use and dementia.