What Does Anticholinergic Do in Simple Terms?

October 8, 2025 •

4 min read

Anticholinergic drugs interfere with how your body uses the neurotransmitter acetylcholine, essentially blocking its communication pathways. This class of medication is used to treat a wide range of conditions by slowing down certain involuntary bodily functions controlled by the nervous system. So, what does anticholinergic do in simple terms? It presses the 'pause' button on some of your body's automatic responses.

Quick Summary

Anticholinergic drugs inhibit the action of the neurotransmitter acetylcholine. This blockade reduces nerve signals that control involuntary muscle movements, secretions, and heart rate, treating conditions from overactive bladder to motion sickness.

Key Points

Blocking Acetylcholine: Anticholinergic drugs work by blocking the neurotransmitter acetylcholine, a key chemical messenger in the nervous system.
Slowing Down 'Rest-and-Digest': This blockade reduces the activity of the parasympathetic nervous system, which controls involuntary functions like digestion and salivation.
Treating Diverse Conditions: Due to their effects, these medications are used for conditions such as overactive bladder, COPD, Parkinson's tremors, and motion sickness.
Common Side Effects: Side effects include dry mouth, blurred vision, constipation, and urinary retention. A mnemonic can help remember them: 'Blind as a bat, dry as a bone,' etc..
Special Caution for Older Adults: Older patients are more vulnerable to severe side effects like confusion, memory problems, and a higher risk of falls, so these drugs should be used cautiously in this population.
Multiple Medications have Effects: Many common medications, including some antihistamines and antidepressants, have anticholinergic properties, sometimes unintentionally.

The Body's Messenger System: Acetylcholine

To understand what anticholinergic drugs do, you first need to know about acetylcholine. Acetylcholine is a neurotransmitter, a chemical messenger that sends signals between nerve cells throughout your body. It plays a critical role in the parasympathetic nervous system, which is responsible for the body's 'rest and digest' functions. Think of it as the system that calms you down after a stressful event. Acetylcholine helps control a variety of involuntary actions, including muscle contractions in the lungs, digestion, urination, and the production of saliva and sweat.

What Does Anticholinergic Do in Simple Terms? The Blockade

At its core, an anticholinergic drug simply blocks acetylcholine from attaching to its receptors on nerve cells. Imagine the acetylcholine message as a key and the nerve receptor as a lock. An anticholinergic drug works like a different key that jams the lock, preventing the real key from being inserted. By blocking this communication, the drug reduces the activity of the parasympathetic nervous system. Instead of being in 'rest and digest' mode, the affected parts of the body slow down.

The Effects on Different Body Systems

Blocking acetylcholine has a ripple effect throughout the body, producing various predictable outcomes. The specific effects depend on where the drug is most active and which receptors it targets. For example, some anticholinergics primarily act on receptors in the bladder, while others have a wider effect. Many over-the-counter medications also have anticholinergic properties as a side effect.

Here are some common systemic effects:

Eyes: Blocking acetylcholine can cause blurred vision and dilated pupils. This is because acetylcholine normally constricts the pupils and helps the eyes focus.
Glands: Salivary and sweat glands are affected, leading to a common side effect: dry mouth and dry skin. This happens because the signals that prompt these glands to secrete are blocked.
Bladder: The muscles of the bladder are relaxed by anticholinergics, which is why these drugs are used to treat conditions like overactive bladder and incontinence. However, this can also lead to urinary retention, making it difficult to fully empty the bladder.
Heart: The heart rate can increase because the nerves that normally slow it down are inhibited.
Digestion: Reduced gastrointestinal motility leads to constipation because the involuntary muscle movements that move food through the digestive tract are slowed.

Common Uses of Anticholinergic Medications

Anticholinergic drugs have a wide range of medical applications due to their ability to modify these involuntary bodily functions. Some of the conditions they are used to treat include:

Overactive Bladder (OAB) and Urinary Incontinence: Medications like oxybutynin and tolterodine relax the bladder muscles, reducing the urgency and frequency of urination.
Chronic Obstructive Pulmonary Disease (COPD) and Asthma: Inhaled anticholinergics, such as ipratropium and tiotropium, relax the muscles around the airways, making breathing easier.
Parkinson's Disease: Anticholinergics like benztropine help reduce tremors and muscle rigidity by balancing brain chemicals that influence movement.
Motion Sickness: Scopolamine is used to prevent nausea and vomiting associated with motion sickness.
Muscle Spasms: They can be used to treat involuntary muscle movements.
Poisoning: Atropine can be an antidote for certain types of poisoning, including nerve gas exposure.
Anesthesia: During surgery, they can be used to control heart rate and reduce salivary and other secretions.

A Comparison: Cholinergic vs. Anticholinergic

It's helpful to compare anticholinergics with their counterpart, cholinergic drugs. While anticholinergics block the action of acetylcholine, cholinergic drugs do the exact opposite—they enhance or mimic its effects.


Feature	Anticholinergic Drugs	Cholinergic Drugs
Mechanism	Block the action of acetylcholine.	Mimic or enhance the action of acetylcholine.
Nervous System Effect	Inhibit the parasympathetic ('rest and digest') system.	Stimulate the parasympathetic ('rest and digest') system.
Pupils	Cause pupil dilation (mydriasis).	Cause pupil constriction.
Saliva/Sweat	Decrease secretions, causing dry mouth and eyes.	Increase secretions, causing excessive salivation.
Heart Rate	Increase heart rate (tachycardia).	Decrease heart rate (bradycardia).
Digestion	Slow down intestinal movement, causing constipation.	Speed up intestinal movement.
Common Uses	Overactive bladder, COPD, Parkinson's tremors.	Alzheimer's disease, glaucoma, myasthenia gravis.

Navigating Side Effects

Because anticholinergics can affect multiple body systems, they can cause a range of side effects. A helpful mnemonic for remembering these is 'Hot as a hare, red as a beet, blind as a bat, dry as a bone, mad as a hatter, and full as a flask'. This refers to the potential for elevated temperature, flushing, blurred vision, dry mouth, confusion/delirium, and urinary retention, respectively.

Risk for Older Adults: Older individuals are particularly susceptible to the side effects of anticholinergics, especially confusion, memory issues, and hallucinations, which can increase the risk of falls. This is why they are often advised to avoid strong anticholinergics. Some long-term studies have also suggested a possible association between cumulative anticholinergic use and an increased risk of dementia, although more research is needed.
Managing Side Effects: If you experience side effects, your doctor may be able to adjust your dose or switch to an alternative medication. It is important to discuss all medications and supplements you take with your healthcare provider, including over-the-counter products, as many have unintended anticholinergic effects.

Conclusion: Important Considerations

In simple terms, anticholinergic drugs work by blocking the action of acetylcholine, a key chemical messenger in the body's nervous system. By doing so, they can effectively treat conditions characterized by excessive muscle activity or secretion. However, this action can also lead to a variety of side effects, including dry mouth, blurred vision, and constipation. For older adults, the risks of cognitive impairment and other adverse effects are particularly significant and require careful consideration. As with any medication, it is essential to use anticholinergics under the careful supervision of a healthcare professional to balance therapeutic benefits against potential risks.

For more detailed information on managing medications, visit the Deprescribing Network website for resources on anticholinergic medications.(https://www.deprescribingnetwork.ca/blog/anticholinergic-medications)

Frequently Asked Questions

The primary action of an anticholinergic drug is to block the neurotransmitter acetylcholine from binding to its receptors on nerve cells. This effectively inhibits the nerve impulses responsible for involuntary functions like muscle contractions and secretions.

Doctors prescribe anticholinergics to treat various conditions by targeting specific involuntary bodily functions. For example, they can relax bladder muscles for overactive bladder, open airways for asthma, or reduce tremors in Parkinson's disease.

Yes, common side effects often include dry mouth, blurred vision, constipation, urinary retention, and increased heart rate. More serious central nervous system effects like confusion or delirium can occur, especially in older adults.

Cholinergic drugs enhance or mimic the effects of acetylcholine, increasing nerve signals. Anticholinergic drugs, on the other hand, block the effects of acetylcholine, inhibiting those same signals.

Yes, long-term use of certain anticholinergics has been associated with an increased risk of cognitive decline, and potentially dementia, particularly in older adults. It is important to discuss these risks with a healthcare provider.

Anticholinergics primarily block nerve impulses in the parasympathetic nervous system, which controls 'rest-and-digest' functions. By doing so, they decrease involuntary actions of smooth muscles in organs like the bladder and lungs.

Yes, many over-the-counter medications, particularly some older antihistamines (like diphenhydramine) and sleep aids, have anticholinergic properties as a secondary effect.