Parasympathomimetic drug

A parasympathomimetic drug is a drug or poison that acts by stimulating or mimicking the parasympathetic nervous system (PSNS). These chemicals are also called cholinergics because acetylcholine (ACh) is the neurotransmitter used by the PSNS. Chemicals in this family can act either directly by stimulating the nicotinic or muscarinic receptors, or indirectly by inhibiting cholinesterase, promoting acetylcholine release, or other mechanisms.

Some chemical weapons such as sarin or VX, non-lethal riot control agents such as tear gas, and insecticides such as diazinon fall into this category.

Direct-acting
These act by stimulating the nicotinic or muscarinic receptors.
 * Choline esters
 * Acetylcholine (all acetylcholine receptors)
 * Bethanechol (M3 receptors)
 * Carbachol (all muscarinic receptors and some nicotinic receptors)
 * Methacholine (all muscarinic receptors)
 * Plant alkaloids
 * Nicotine
 * Muscarine
 * Pilocarpine (M3 receptors)

Indirect-acting
Indirect acting parasympathomimetic drugs may be either reversible cholinesterase inhibitors, irreversible cholinesterase inhibitors or drugs that promote ACh release or Anti-adrenergic. The latter inhibits the antagonistic system, the sympathetic nervous system.
 * Reversible cholinesterase inhibitors
 * Donepezil
 * Edrophonium
 * Neostigmine
 * Physostigmine
 * Pyridostigmine
 * Rivastigmine
 * Tacrine
 * Irreversible cholinesterase inhibitors
 * Echothiophate
 * Isoflurophate
 * Malathion
 * ACh release promoters
 * Cisapride
 * Metoclopramide
 * Anti-adrenergics
 * clonidine (α-receptor agonist, α2 > α1, giving negative feedback)
 * propranolol (β2 antagonist)
 * atenolol (β1 antagonist)
 * prazosin (α1 antagonist)
 * methyldopa (α2 agonist giving negative feedback)