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Classification

First of let’s see how drugs can be targeted at cholinergic receptors. Since acetylcholine act at two receptors such as

Muscarinic
Nicotinic

Drugs can act in two ways

Muscarinic antagonists
Nicotinic antagonists

classification of cholinergic antagonists

Muscarinic antagonists

Muscarinic receptors are further classified into M1 to M5 and drugs may produce either selective or non-selective block. Based on that we can divide this category further into

Non-selective muscarinic antagonists
Selective muscarinic antagonists

Non-selective muscarinic antagonists

This category includes various drugs like

Atropine
Scopolamine
Dicyclomine
Cyclopentolate
Tropicamide
Ipratropium
Tiotropium
Solifenacin
Oxybutynin
Tolterodine
Benztropine
Trihexyphenidyl

Selective muscarinic antagonists

Selective cholinergic antagonists are available on M1, M2 and M3 receptors.

M1 antagonist
- Pirenzepine
M2 antagonist
- Gallamine
M3 antagonist
- Darifenacin

Note: Gallamine is a M2 blocker as well as neuromuscular blocker.

Nicotinic antagonists

For simple understanding we have named them as nicotinic antagonists, but practically they are classified as ganglionic and neuromuscular blockers.

Drug targets block nicotinic receptors mainly at two locations such as autonomic ganglia and neuromuscular junction. Hence two category of drugs acting on these receptors are

Ganglionic blockers
Neuromuscular blockers

Ganglionic blockers

Many drugs acting in this category have little clinical indications today. Drugs acting somewhat selectively on ganglia include

Hexamthonium
Trimethaphan

Few drugs acting at these receptors are not completely selective and show little action at other locations like neuromuscular junction. For example, d-tubocurarine acts both as ganglionic blocker and neuromuscular blocker.