Which Common Medicines Have Anticholinergic Effects That Can Cloud Memory?

Common medicines with anticholinergic effects include first-generation antihistamines such as diphenhydramine (Benadryl), many "PM" sleep aids, some bladder medicines such as oxybutynin, and older antidepressants such as amitriptyline. They block acetylcholine, a brain and body messenger, and in older adults may contribute to confusion, forgetfulness, dry mouth, constipation and falls. Sudden confusion needs urgent evaluation. This article lists examples, explains the warning signs, and shows how to review your list with a pharmacist.

Which common medicines have anticholinergic effects?

Acetylcholine is a chemical messenger that helps nerves talk to muscles, glands and the brain. Anticholinergic medicines block it. Sometimes that blockade is the point of the drug, such as calming an overactive bladder. In other cases it is a side effect of a drug designed for something else. Many of these products are sold over the counter, so they may not appear on a prescription list.

The groups below are the ones older adults most often meet. Strength varies a great deal between drugs, even inside one group, so this list is a starting point for a conversation and not a verdict on any single medicine.

Allergy, cold and sleep products

• Diphenhydramine (Benadryl, and the "PM" versions of pain relievers and cold products)
• Doxylamine (Unisom SleepTabs, and some nighttime cold and flu liquids)
• Chlorpheniramine (found in several multi-symptom cold products)
• Hydroxyzine and promethazine (prescription, used for itching, nausea or anxiety)

Newer allergy tablets such as loratadine, cetirizine and fexofenadine are generally considered less anticholinergic, though cetirizine can still cause drowsiness. A pharmacist can help you compare options for your situation.

Bladder medicines

Oxybutynin, tolterodine, solifenacin, darifenacin, trospium and fesoterodine treat overactive bladder by relaxing bladder muscle. Oxybutynin is often discussed as one of the more brain-active members of the group, but all of them can cause dry mouth and constipation. Some bladder medicines work through a different pathway and do not carry the same concern, so it can be worth asking your prescriber whether an alternative fits you.

Antidepressants

Older tricyclic antidepressants such as amitriptyline, nortriptyline, imipramine and doxepin have notable anticholinergic activity. Paroxetine is the SSRI most often named for this effect. Antidepressant labels carry a boxed warning about increased suicidal thoughts and behavior in children, teenagers and adults up to age 24, and any change in mood or behavior after starting or adjusting one deserves a prompt call to the prescriber. Do not stop or change the dose of an antidepressant on your own, because stopping suddenly can cause its own problems.

Muscle, stomach, motion-sickness and movement medicines

• Cyclobenzaprine (a muscle relaxant)
• Dicyclomine and hyoscyamine (stomach and bowel cramp medicines)
• Meclizine and scopolamine patches (dizziness and motion sickness)
• Benztropine and trihexyphenidyl (used for tremor or movement side effects)

Antipsychotics and others

Some antipsychotics, including olanzapine, clozapine and to a lesser degree quetiapine, have anticholinergic activity. Antipsychotic labels carry a boxed warning about higher risk of death when used in older adults with dementia-related psychosis. Clozapine has additional label warnings and requires regular blood-count monitoring, and it should not be stopped or changed without the prescriber. Only the prescribing clinician can weigh whether a given medicine is still the right choice.

Inhalers

Inhaled anticholinergics such as ipratropium and tiotropium are used for COPD. Because the dose is delivered to the lungs, they are generally thought to reach the brain much less than a tablet does. They can still worsen narrow-angle glaucoma or urinary retention in susceptible people, so tell your clinician if you have either condition. Do not stop a breathing medicine without talking to the clinician who prescribes it.

How can these medicines cloud memory and thinking?

Acetylcholine helps the brain with attention, learning and forming new memories. When a medicine blocks it, a person may feel foggy, slowed down, forgetful or drowsy. Older adults can be more sensitive for several reasons: the body may clear drugs more slowly with age, the brain may have less acetylcholine reserve to start with, and many older adults take several medicines at once.

That last point matters. Anticholinergic effects can add up. A bladder pill, a nighttime allergy tablet and an older antidepressant may each seem mild, yet together they create a larger "burden." Researchers use the term anticholinergic burden for this combined load.

What the research suggests

Several studies indexed on NIH's PubMed Central have looked at this. A cohort study of anticholinergic medication burden in older adults examined its link with later dementia and stroke, and a study using the UK Biobank and the All of Us research program examined an anticholinergic medication index and dementia risk. These studies describe an association. Observational research cannot show that the medicines caused dementia, because people may take these drugs for conditions or early symptoms that themselves relate to memory change. Researchers are still working out how much of the link is direct drug effect, how much depends on dose and duration, and how much comes from other factors.

The practical message is modest and useful: if a lower-risk alternative exists, it is reasonable to ask whether you need the higher-risk one.

Other signs an anticholinergic medicine may be affecting you

Memory trouble is only one possible clue. Anticholinergic effects often show up across the body, and noticing them can help your clinician spot the pattern.

• Dry mouth and dry eyes. Less saliva and tears. See our article on medications that can cause dry mouth for more on this effect.
• Constipation. The bowel slows down, and in some people this can become severe.
• Trouble urinating. Hesitancy, a weak stream or feeling unable to empty the bladder, especially in people with an enlarged prostate.
• Blurred vision. The pupil may widen and focusing can become harder.
• Fast heartbeat, flushing or feeling overheated. The body may sweat less.
• Dizziness, drowsiness and unsteadiness. These can raise the chance of a fall.

MedlinePlus notes that falls are a serious concern for older adults and that some medicines can contribute to them, and its dizziness and vertigo page lists medicines among the possible causes of lightheadedness. A fall in someone newly started on one of these drugs is worth mentioning to the prescriber.

Confusion that comes on suddenly is different

A slow drift in memory over months calls for a planned visit. Sudden or rapidly worsening confusion is different, and it needs same-day medical evaluation, with emergency care if it comes with any stroke sign. Delirium is an abrupt state of confusion that can come from infection, dehydration, a new medicine, a stroke or other illness. Anticholinergic medicines are among the possible contributors, but they are not the only one, and a person who becomes suddenly confused needs a clinician to look for the cause.

Stroke signs come first. Face drooping, arm weakness, slurred speech or sudden trouble seeing are 911 situations, even if the person recently took a drug that could explain some of the symptoms. Taking too much of an anticholinergic product, including a double dose of a nighttime cold remedy or an overdose, can produce hot dry skin, agitation, hallucinations and a racing heart, and needs emergency help.

How to review your list without making risky changes

You do not need to give up everything on the lists above. Some of these medicines do a job that matters, and stopping certain ones suddenly can cause harm. The safer approach is a review with the people who know your history.

1. Make a full list. Include prescriptions, over-the-counter products, sleep aids, allergy pills, patches, eye drops and supplements. Bring the bottles to the visit if you can.
2. Check labels for the usual names. Diphenhydramine and doxylamine appear in many products that do not say "allergy" on the front. A "PM" label is a clue.
3. Ask a pharmacist for a medication review. Pharmacists can often flag which items carry anticholinergic effects and which may overlap.
4. Tell your prescriber about memory, bowel, bladder and vision changes so they can decide whether a different medicine, a different dose or a non-drug approach is appropriate. Please do not adjust timing or dose of a prescription yourself.
5. Ask about alternatives for the problem the drug treats. For sleep, bladder urgency, allergies or nausea, options with less anticholinergic activity and non-drug measures may exist. Our article on prescription sleep pills covers the sleep side, and our gabapentin article covers another medicine that can cause drowsiness in older adults.

A randomized trial of the Care Ecosystem collaborative dementia care program, published on PubMed Central, examined potentially inappropriate medication use. It does not by itself show that a home medication list prevents harm, but it illustrates that structured medication review is something care teams actively work on. Keeping an updated list can help clinicians review medicines.

If a family member has dementia and is on one of these drugs, ask the prescriber whether the benefit still outweighs the risk, since anticholinergic drugs can oppose the action of cholinesterase inhibitors used for memory loss, and a pharmacist or prescriber should review the combination. Planning ahead for decisions about care is also worthwhile; our advance directive article explains how.

Who should be most careful

• Adults with existing memory problems or a dementia diagnosis.
• People who take many medicines, including several that cause drowsiness.
• Anyone with narrow-angle glaucoma, an enlarged prostate with urinary trouble, or significant constipation, because anticholinergics can worsen these.
• People with a history of falls or unsteadiness.
• People with kidney or liver conditions, since drugs may linger longer in the body.

MedlinePlus's older adult health and older adult mental health pages are a good place to read more about staying well as medicines and needs change.

When to Seek Medical Care