• Clinical science

Parasympathomimetic drugs (Cholinomimetic drugs)

Abstract

Parasympathomimetic drugs activate the parasympathetic nervous system (PSNS). As the neurotransmitter of the PSNS is acetylcholine, parasympathomimetics are also called cholinomimetic agents. These are classified according to whether they act as direct agonists of acetylcholine receptors (ACh) or indirect agonists of ACh (also called anticholinesterase). While direct agonists act by binding directly to muscarinic or nicotinic ACh receptors, indirect agonists prolong the action of endogenous acetylcholine by inhibiting acetylcholinesterase. Direct agonists of ACh are used topically in ophthalmology to induce miosis, while indirect agonists are used to treat, e.g., postoperative ileus or urinary retention and myasthenia gravis.

Overview

Drug Indications
Direct parasympathomimetics (direct agonist)
  • Induces sweat, tears, and saliva production
  • Open-angle and closed-angle glaucoma
Indirect parasympathomimetics (indirect agonist)

Effects

Effects of parasympathomimetics

ACh receptors Organ/Tissue Effects
M1, M4, M5

Central nervous system

  • Influences neurologic functions (e.g., memory)
M2

Heart

  • Heart rate and atrial contractility
  • Slows down AV conduction → possibly AV block
M3

Smooth muscle

Exocrine glands

Nicotinic Skeletal muscle
  • ↑ Muscle contraction and tone

References:[1]

Side effects

Direct parasympathomimetics

Indirect parasympathomimetics

DUMBBELSS for clinical features of cholinesterase inhibitor poisoning = Diarrhea, Urination, Miosis, Bronchospasm and Bradycardia, Neuromuscular Excitation, Lacrimation, Sweating and Salivation!

References:[2]

We list the most important adverse effects. The selection is not exhaustive.