Cholinergic vs Anticholinergic: Pharmacology Made Easy

Cholinergic and anticholinergic drugs are among the most common drugs administered to patients. Therefore, recognizing the key differences between cholinergic vs anticholinergic is a vital nursing responsibility in medication administration.

Cholinergic drugs stimulate the parasympathetic system and increase the acetylcholine released into the synapse (which is a structure that permits a neuron to pass an electrical or chemical signal to another neuron). This can cause fight or flight.

Anticholinergic drugs oppose (or reduce) the effects of cholinergic drugs. They work by blocking acetylcholine receptors or preventing the release of acetylcholine into the synapse. In the simplest sense, anticholinergics are drugs that can turn off the system in your body that causes the fight and flight reaction.

Sympathetic vs Parasympathetic Nervous Systems

The sympathetic nervous system signals it’s time for battle, while the parasympathetic system signals it’s time to relax. Cholinergic drugs create relaxation by producing more acetylcholine, the neurotransmitter that helps muscles contract. Anticholinergics increase reactivity by blocking the receptors that acetylcholine binds to.

How do you differentiate SNS from PNS?

• Sympathetic nervous system (SNS) – fight and flight
• Parasympathetic nervous system (PNS) – rest and digest

When trying to compare and contrast one from the other, consider these questions:

1. Where is the blood going?
2. Is it headed towards your fight and flight organs or towards your digest and rest organs?
3. What are your fight and flight organs?
4. What are your rest and digest organs?

Your fight and flight organs are:

• Heart
• Lungs
• Brain

Your rest and digest organs are:

• Gastrointestinal (GI) Tract
• Kidneys
• Muscles
• Other organs

Want to learn more about neurological drugs? Read our NCLEX review here.

Teeter-Totter Figure Memory Trick

To make your memorization easier, imagine a teeter-totter.

On the left side, is the sympathetic nervous system (SNS), and on the right is the parasympathetic nervous system (PNS) or the parasympathomimetic nervous system.

Below your SNS, write down the organs responsible for the fight and flight reaction: the heart, lungs, and brain. Then below the PNS, write down the organs responsible for the rest and digest reaction: the GI tract, kidneys, and muscles.

Cholinergic vs Anticholinergic

After identifying what the SNS and PNS are, relate them to cholinergic and anticholinergic drugs.

If a client takes an anticholinergic drug, it could be harmful if they take any cholinergic drugs simultaneously.

For example, if a client takes an anticholinergic drug and then is diagnosed with cancer (which could require chemotherapy or radiation treatment), the drugs used during those treatments could make the client critically ill if they have been prescribed an anticholinergic medication beforehand.

What are anticholinergic drugs?

Anticholinergic drugs are a group of medications that block the effects of acetylcholine in the body. They are typically used to manage symptoms of Alzheimer’s disease and dementia.

The mechanism of anticholinergic drugs is to direct blood to the heart, lungs, and brain by inhibiting the parasympathetic nervous system. When the signal going to the PNS is blocked or disrupted, involuntary functions like mucus secretion, salivation, urination, and digestion is decreased significantly.

Anticholinergic Side Effects

• Dry mouth
• Blurred vision
• Constipation
• Urinary retention
• Increased heart rate
• Drowsiness
• Cognitive impairment
• Confusion
• Dry eyes
• Skin flushing

List of Anticholinergic Drugs

• Benzatropine
• Atropine
• Epinephrine
• Cyclopentolate

A very useful tip when remembering cholinergic and anticholinergic drugs. Just remember the 3 S’s:

• See
• Spit
• Shit (excrete)

To put it another way:

• Cholinergics – can see, can spit, can shit
• Anticholinergics – can’t see, can’t spit, can’t shit

Easy enough? Cholinergic agents allow the production of fluid that moisturizes the eyes, and increases salivation, urination, and defecation.

Anticholinergic agents decrease all the activities mentioned above. Instead, you will increase the client’s heart rate and perfusion to the lungs and brain.

So just remember, administering drugs with SNS and PNS effects will directly influence where the blood will be heavily distributed to treat several conditions. If you turn one off, the other is turned on. Don’t forget the teeter-totter figure.

What are cholinergic drugs?

Cholinergic drugs are a class of medications that work by activating the muscarinic receptors in the body’s parasympathetic nervous system. These receptors regulate involuntary functions like heart rate, salivation, and digestion.

They are basically the opposite of the SNS. Because with cholinergic drugs, there is an increase in involuntary functions which means that there is saliva production, urination, and mucus secretion.

Cholinergic drugs are commonly used to treat diseases like Alzheimer’s, glaucoma, paralytic ileus, and Parkinson’s.

Cholinergic Side Effects

• Increased salivation
• Sweating
• Nausea and vomiting
• Diarrhea
• Abdominal cramps
• Increased urinary frequency
• Dizziness
• Low blood pressure
• Bronchoconstriction
• Increased secretions

List of Cholinergic Drugs

• Bethanechol
• Ambenonium chloride
• Methacholine
• Carbachol

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