What Are Anticholinergic Medications?

Ancient civilizations smoked the Datura plant seeking religious visions. Little did they know that centuries later, this plant would form the basis of a new class of medications known as anticholinergics.

Anticholinergics are a broad group of medications that treat medical conditions such as nausea, irritable bowel syndrome, and eye problems. Over 600 medications have some degree of anticholinergic activity. But what makes a medication anticholinergic, and how do they work?

What are anticholinergic medications?

Anticholinergic medications block a chemical called acetylcholine in the body. Acetylcholine is a neurotransmitter (chemical messenger). It attaches to different sites in the body to deliver messages from one nerve cell to another.

Acetylcholine regulates many bodily functions, including:

• Muscle contraction (including heart muscle)

• Heart rate

• Blood pressure

• Secretions (like sweat and saliva)

• Erections

• Moving food through your digestive system

• Memory and attention

How do anticholinergic medications work?

Acetylcholine works by attaching to two main types of receptors (binding sites). These are called muscarinic receptors and nicotinic receptors. Anticholinergic medications work by blocking acetylcholine from attaching to these receptors. Most anticholinergic medications mainly block muscarinic receptors. That’s why sometimes they’re also called “antimuscarinics”.

There are at least five different types of muscarinic receptors. They’re located in many areas of the body, including the:

• Brain

• Eyes

• Salivary glands

• Sweat glands

• Heart

• Lungs

• Gastrointestinal system (stomach and intestines)

• Bladder

Because muscarinic receptors are found in so many places, anticholinergics can affect many different parts of the body. This makes them effective for a number of different health conditions.

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Cholinergic vs. anticholinergic medications: What’s the difference?

Cholinergic medications do the exact opposite of anticholinergic medications. They increase acetylcholine levels instead of blocking its effect. Cholinergic medications are most often used to treat myasthenia gravis or dementia associated with Alzheimer’s disease.

The easiest way to compare cholinergic versus anticholinergic medications is to look at how they each affect different parts of the body. We compare those effects in the table below.

Good to know: Cholinergic and anticholinergic medications won’t always cause the listed symptoms. This is meant as a general comparison to show the differences between their potential effects.

What do anticholinergic medications treat, and what are some common examples?

Anticholinergic medications are used to treat multiple medical conditions. Some examples are detailed in the table below.

Other medications may have anticholinergic effects that aren’t related to the conditions they treat. Instead, the anticholinergic activity is responsible for some of the side effects of the medication. Some common examples of this are:

• Antipsychotic medications like clozapine (Clozaril) and quetiapine (Seroquel)

• Tricyclic antidepressants (TCAs) like nortriptyline (Pamelor), doxepin, and amitriptyline

• First-generation antihistamines like diphenhydramine (Benadryl) and doxylamine (Unisom)

What are common side effects of anticholinergic medications? 

As with all medications, anticholinergic medications may cause side effects. Some of these side effects can cause serious problems, especially for older people.

The side effects of anticholinergics may include:

• Memory problems and confusion

• Dry mouth

• Sweating less

• Rapid heart rate

• Constipation

• Less tear production

• Trouble urinating

• Blurry vision

• Dilated pupils

• Narrow-angle glaucoma

When should I contact my healthcare provider about anticholinergic side effects?

If any anticholinergic side effects become bothersome or severe, be sure to let your healthcare provider know. They may be able to adjust your dose or medication to manage your symptoms.

In rare cases, toxicity can occur from anticholinergic medications. You can use the memory device below to help remember the various symptoms:

• Red as a beet (flushing of the skin)

• Dry as a bone (dry mouth, eyes, and skin)

• Blind as a bat (dilated pupils)

• Mad as a hatter (confusion, delirium, agitation)

• Hot as a hare (overheating and fever)

• Full as a flask (trouble peeing)

If you or a loved one develops symptoms of anticholinergic toxicity, call 911 or seek emergency care. You can also contact Poison Control at 1-800-222-1222.

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Written by:

Sarah Lobello Pearson, PharmD

Sarah Pearson is a practicing pharmacist with over 10 years of experience in the field. She received her doctorate in pharmacy from the University of Georgia in Athens, GA.

Edited by:

Stacia Woodcock, PharmD

Stacia Woodcock, PharmD, is a pharmacy editor for GoodRx. She earned her Doctor of Pharmacy degree from the University of Kentucky and is licensed in New York and Massachusetts.

Reviewed by:

Christina Aungst, PharmD

Christina Aungst, PharmD, is a pharmacy editor for GoodRx. She began writing for GoodRx Health in 2019, transitioning from freelance writer to editor in 2021.

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