Cholinomimetics are a class of drugs that increase the activity in cholinergic neurons. They are called cholinomimetics because they mimic the action of acetylcholine. There are two main targets of drug action: the postsynaptic receptor and the acetylcholinesterase enzyme, which breaks down acetylcholine.
Cholinomimetic drugs= Cholinergic agonists + Cholinesterase inhibitors.
The cholinesterase inhibitors increase the activity of cholinergic neurons by blocking the enzyme acetylcholinesterase which metabolizes or breaks down acetylcholine. As such, cholinesterase inhibitors block the metabolism of acetylcholine. Cholinesterase inhibitors effectively increase the concentration of acetylcholine at all cholinergic synapses.
Cholinesterase inhibitors
| Reversible Inhibitors | Irreversible Inhibitors | |
|---|---|---|
| Myasthenia Gravis | Alzheimer Disease | |
|
EDROPHONIUM NEOSTIGMINE PYRIDOSTIGMINE ambenonium demecarium physostigmine |
DONEPEZIL galantamine RIVASTIGMINE |
diisopropyl fluorophosphate echothiophate isoflurophate malathion parathion sarin soman |
Anticholinergics
Anticholinergics are also called cholinergic antagonists, cholinergic blockers, or parasympatholytics drugs.
They antagonize the effects of acetylcholine. “Most of these drugs are antagonists directly at the nicotinic or muscarinic receptor. Some act on the ion channel associated with the nicotinic receptor, and still others block acetylcholine release.”
What is the difference between anticholinergics and cholinesterase inhibitors?
Cholinesterase inhibitors increase the amount of acetylcholine and its effects. Anticholinergics block acetylcholine and stop it from working!
It is not advisable to use anticholinergics in a patient who is on cholinesterase inhibitors.
Reference:
“Cholinergic Agonists.” Basic Concepts in Pharmacology: What You Need to Know for Each Drug Class, 5e Ed. Janet L. Stringer. New York, NY: McGraw-Hill,