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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.

Neuromuscular blockers

Neuromuscular blockers can act in two ways such as depolarising and non-depolarising. Various drugs included in these categories are

  • Depolarising
  • Non-depolarising
classification of neuromuscular blockers

Depolarising neuromuscular blockers

Depolarising neuromuscular blocker includes only one drug, that is, suxamethonium.

Note: Suxamethonium is also called as succinylcholine.

Non-depolarising neuromuscular blockers

This category includes several drugs and many of the drugs are structurally derived from the natural curare alkaloid.

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