What is the Difference Between Cholinergic and Anticholinergic

Cholinergic and anticholinergic drugs are basically opposites in how they affect the nervous system, particularly in relation to the neurotransmitter acetylcholine (ACh).

What is the difference between cholinergic and anticholinergic? Cholinergic enhances the effects of ACh, while anticholinergic blocks the action of ACh.

Key Areas Covered

1. What is Cholinergic  
      – Definition, Features 
2. What is Anticholinergic
      – Definition, Features 
3. Similarities Between Cholinergic and Anticholinergic 
      – Outline of Common Features
4. Difference Between Cholinergic and Anticholinergic
      – Comparison of Key Differences
5. FAQ: Cholinergic and Anticholinergic
      – Answers to Frequently Asked Questions

Key Terms

Cholinergic, Anticholinergic, Acetylcholine

What is Cholinergic

Cholinergic drugs are a category of medications that influence the nervous system by interacting with acetylcholine (ACh), which is a neurotransmitter. In fact, there are two types of cholinergic drugs. They are direct-acting agonists and indirect-acting cholinesterase inhibitors.

Direct-acting agonists directly bind to and activate the receptors for ACh, replicating the conductor’s actions. Furthermore, examples of these kinds of drugs include pilocarpine, which is used to treat glaucoma by stimulating tear production, and bethanechol, which helps with urinary retention.

Indirect-acting cholinesterase inhibitor drugs don’t directly mimic ACh. They protect the existing ACh in the body. Moreover, examples include Donepezil and rivastigmine, which are used for Alzheimer’s disease, as they can enhance memory function by promoting ACh activity.

Figure 1: Acetylcholine

The effect of cholinergic drugs depends on the part of the nervous system they target. They mainly influence the parasympathetic nervous system. Though there are advantages to cholinergic drugs, there are also side effects. These may include nausea, vomiting, diarrhea, or difficulty breathing.

Cholinergic drugs are used to treat a variety of conditions, including Myasthenia gravis, a neuromuscular disease, glaucoma, to increase drainage of fluid from the eye, and Alzheimer’s disease, to improve cognitive function.

What is Anticholinergic

Anticholinergic drugs work opposite to cholinergic drugs by blocking the action of acetylcholine. There are two main types of anticholinergic drugs. They are antimuscarinic drugs and nicotinic antagonists.

Antimuscarinic drugs target muscarinic receptors, which are abundant in the PNS. Blocking these receptors leads to decreased activity in organs controlled by the PNS (peripheral nervous system), like the bladder, intestines, and airways. Additionally, examples include oxybutynin, used for overactive bladder, and diphenhydramine, an antihistamine that can cause drowsiness.

Nicotinic drugs target a different type of ACh receptor (nicotinic) found at neuromuscular junctions and in the central nervous system. They are less commonly used but can have effects like muscle weakness and confusion.

The overall effects of anticholinergic drugs depend on which receptors they block. Moreover, examples of such effects are increased heart rate, dry mouth, eyes, and skin, relaxation of smooth muscles, leading to constipation and urinary hesitancy (difficulty starting urination), and dilation of the pupils. Anticholinergics can also cause side effects like dizziness, confusion, and memory problems, especially in older adults.

Some conditions treated with anticholinergics include overactive bladder, chronic obstructive pulmonary disease (COPD), motion sickness, and Parkinson’s disease (to manage tremors).

Similarities Between Cholinergic and Anticholinergic

1. Both drug classes revolve around ACh.
2. These types of drugs can have overlapping side effects on the nervous system.
3. Both cholinergic and anticholinergic drugs find uses in treating conditions affecting the nervous system, particularly the parasympathetic nervous system (PNS).

Difference Between Cholinergic and Anticholinergic

Definition

• Cholinergics are the substances that enhance the effects of ACh, while anticholinergics are the substances that block the action of ACh.

Nature

• Cholinergic drugs promote slowing down, digestion, secretions (sweat, tears, saliva), and muscle contraction, while anticholinergic cause speeding up, dilation (pupils), dryness (mouth, eyes), and relaxation of muscles.

Side Effects

• Side effects of cholinergic drugs include nausea, vomiting, diarrhea, and difficulty breathing, whereas side effects of anticholinergic drugs include dizziness, confusion, memory problems, constipation, and urinary hesitancy.

Applications

• Cholinergic drugs are used for myasthenia gravis, glaucoma, and Alzheimer’s disease, while anticholinergic drugs are used for overactive bladder, COPD, motion sickness, and Parkinson’s disease (tremors).

Conclusion

Cholinergic and anticholinergic drugs are basically opposites in how they affect the nervous system. The main difference between cholinergic and anticholinergic is that cholinergic enhances the effects of ACh while anticholinergic blocks the action of ACh.

FAQ: Cholinergic and Anticholinergic

1. What is the difference between the two types of cholinesterase?

There are two main cholinesterases: acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). AChE is much faster and specializes in nerve signals, while BChE is found in blood plasma and acts more like a cleanup crew.

2. What are examples of Cholinergics?

There are two main types of cholinergic: direct-acting and indirect-acting. Direct-acting cholinergic mimic acetylcholine, binding directly to receptors. Examples include acetylcholine (ACh), which is a natural neurotransmitter. Indirect-acting cholinergics inhibit acetylcholinesterase, the enzyme that breaks down ACh, making more available. An example is Donepezil, which is used to treat Alzheimer’s disease.

3. Why is it called cholinergic?

It’s called cholinergic because it works with acetylcholine (ACh). “Cholinergic” comes from “choline,” a part of ACh, and “ergic” meaning “related to work.” So, cholinergic refers to anything that uses or affects ACh.

4. What is the use of anticholinergic drugs?

Anticholinergic drugs block acetylcholine, a neurotransmitter. This calms overactive muscles in conditions like:

• Overactive bladder
• COPD (breathing problems)
• Stomach cramps
• Parkinson’s tremors

5. Is amoxicillin anticholinergic?

Amoxicillin is not typically considered a strong anticholinergic. Some studies show minimal anticholinergic effects at very high doses.

Reference:

1. “Cholinergic Drug.” Encyclopedia Britannica.
2. “Anticholinergic.” Science Direct.

Image Courtesy:

1. “Acetylcholine” By Harbin – Own work (Public Domain) via Commons Wikimedia