Cholinergic Drugs

Cholinergic drugs are also called parasympathomimetics because their effect mimics the effect of parasympathetic nerve stimulation. Administration of these drugs will result in an increase in the parasympathetic activities in the systems innervated by cholinergic nerves.

There are two groups of cholinergic drugs:

1. Direct-acting: bind to and activate muscarinic or nicotinic receptors (mostly both) and include the following subgroups:
   1. Esters of choline: methacholine, carbachol, betanechol
   1. Cholinergic alkaloids: pilocarpine, muscarine, arecoline, nicotine
2. Indirect-acting: inhibit the action of acetylcholinesterase enzyme
   1. Reversible: neostigmine, physostigmine, edrophonium
   1. Irreversible: Organophosphate compounds; echothiophate

The actions of acetylcholine may be divided into two main groups: –

1. Nicotinic actions- those produced by stimulation of all autonomic ganglia and the neuromuscular junction
2. Muscarinic actions- those produced at postganglionic cholinergic nerve endings