Drug Acting on G.I. System - Cholinergic, Anticholinergics

Drug Acting on G.I. System

Cholinergic

Anticholinergics

Proton pump  inhibitors

Antiemetics

Emetics

Purgatives

Antacids

Fluid and Electrolyte therapy 

Antidiarrheals

Histamines

Cholinergic Drug

Parasympathomimetic or cholinomimetics

Stimulate parasympathetic nervous system in same manner as does acetylcholine

May stimulate cholinergic receptors directly or slow acetylcholine metabolism at synapses (Affect the enzyme acetylcholinesterase)

Useful in treating Alzheimer’s disease, Myasthenia gravis and to treatment atony of the smooth muscle of the GI system or urinary system.

GI effects

Acetylcholine stimulates cholinergic receptors in the gut to promote normal secretory and motor activity

Cholinergic activity in the gut will increase peristalsis and facilitates movement of flatus and feces.

The secretory functions of the salivary and gastric glands also stimulated.

Increased tone and contractility in GI smooth muscle, relaxation of sphincters, increased salivary gland and GI secretions.

Anticholinergics

Also called cholinergic blocking agents or parasympatholytics Again, focus is on the parasympathetic nervous system

Parasympathetic system acts as a resting and reparative function Functions include digestion, excretion, cardiac decelertion, and anabolism and near vision.

Most anticholinergic drugs interact with the muscarinic receptors in the brain, secretory glands, heart, and smooth muscle.

A few can also affect the nicotinic receptors. 

Glycopyrrolate (Robinul) is an example

Mechanism of action:

Act by occupying receptor sites at parasympathetic nerve endings, thereby leaving fewer receptor sites free to respond to acetylcholine.

Distribution of receptors is broad so effect of anticholinergics will be diffuse.

Helpful in treating irritable colon or colitis.

Useful in gastritis, pylorospasm and ulcerative colitis as they slow motility.