A parasympathomimetic drug, sometimes called a cholinomimetic drug[1] or cholinergic receptor stimulating agent,[2] is a substance that stimulates the parasympathetic nervous system (PSNS).[3][2] These chemicals are also called cholinergic drugs because acetylcholine (ACh) is the neurotransmitter used by the PSNS.[1][4] Chemicals in this family can act either directly by stimulating the nicotinic or muscarinic receptors (thus mimicking acetylcholine), or indirectly by inhibiting cholinesterase, promoting acetylcholine release, or other mechanisms.[5] Common uses of parasympathomimetics include glaucoma, Sjögren syndrome and underactive bladder.[6]
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.
For a cholinergic agent, the following criteria describe the structure activity relationship:
These act by stimulating the nicotinic or muscarinic receptors.
Indirect acting parasympathomimetic substances may be either reversible cholinesterase inhibitors, irreversible cholinesterase inhibitors or substances that promote ACh release or anti-adrenergics. The latter inhibits the antagonistic system, the sympathetic nervous system.