Parasympathomimetic drug

Parasympathomimetic drug

A parasympathomimetic drug, sometimes called a cholinomimetic drug, is a substance that stimulates the parasympathetic nervous system (PSNS).[1] These chemicals are also called cholinergic drugs 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 (thus mimicking acetylcholine), or indirectly by inhibiting cholinesterase, promoting acetylcholine release, or other mechanisms. [2]

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.


  • Structure activity relationships for parasympathomimetic drugs 1
  • Pharmaceuticals 2
    • Direct-acting 2.1
    • Indirect-acting 2.2
  • See also 3
  • Notes 4
  • External links 5

Structure activity relationships for parasympathomimetic drugs[3]

For a cholinergic agent, the following criteria describe the structure activity relationship:

  1. Ing's Rule of 5: There should be no more than five atoms between the nitrogen and the terminal hydrogen for Muscarinic (or cholinergic) activity.
  2. molecule must possess a nitrogen atom capable of bearing a positive charge, preferably a quaternary ammonium salt.
  3. for maximum potency, the size of the alkyl groups substituted on the nitrogen should not exceed the size of a methyl group.
  4. The molecule should have an oxygen atom, preferably an ester-like oxygen capable of participating in a hydrogen bond.
  5. There should be a two-carbon unit between the oxygen atom and the nitrogen atom.



These act by stimulating the nicotinic or muscarinic receptors.


Indirect acting parasympathomimetic drugs may be either reversible cholinesterase inhibitors, irreversible cholinesterase inhibitors or drugs that promote ACh release or anti-adrenergics. The latter inhibits the antagonistic system, the sympathetic nervous system.

See also: alpha blocker and beta blocker

See also


  1. ^ "Dorlands Medical Dictionary:parasympathomimetic". 
  2. ^ Brenner, G. M. (2000). Pharmacology. Philadelphia, PA: W.B. Saunders Company. ISBN 0-7216-7757-6
  3. ^ Medicinal Chemistry of Adrenergics and Cholinergics
  4. ^ Karadsheh, N; Kussie, P; Linthicum, DS (1991). "Inhibition of acetylcholinesterase by caffeine, anabasine, methyl pyrrolidine and their derivatives". Toxicology letters 55 (3): 335–42.  
  5. ^ Pohanka, M (2014). "The effects of caffeine on the cholinergic system.". Mini Reviews in Medicinal Chemistry 14 (6): 543–549.  

External links