Acetylcholine

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Acetylcholine is the prototypical cholinergic agent. It functions as a neurotransmitter at all cholinergic sites in the body

[edit] PHARMACOKINETICS

  • Acetylcholine is poorly absorbed from the gastric mucosa; therefore it is ineffective if given orally. Choline esters (metacholine, carbachol and betanechol) are synthetic derivatives of choline with longer duration of action and can be given orally as well as parenterally.
  • The recommended way of administration is parenteral.
  • In the blood it is rapidly hydrolyzed by the enzyme cholinesterase into acetic acid and choline; this makes its duration of action very short and unreliable for therapeutic purposes

[edit] PHARMACODYNAMICS

Acetylcholine can act on nicotinic and muscarinic receptors

ORGAN
EFFECTS
Heart
slow heart rate and decrease the contractile force (M2 receptors)
Blood vessels
Vasodilatation and drop in blood pressure
Gastrointestinal tract
It increases the gastrointestinal motility and secretion of gastric acid (M1 Receptors)
Urinary tract
It stimulates the detrusor muscle and relaxes the internal urethral sphincter resulting in evacuation of bladder (M3 receptors)
Bronchioles
Bronchoconstriction
Eye
miosis and accommodation for near objects because of stimulation of the constrictor pupillae and ciliary muscles respectively (M3 receptors)
Exocrine glands
it stimulates salivary, gastric, bronchial, lachrymal and sweat gland secretions (M3 receptors)