Some cholinergic drugs like,
Methacholine, carbachol, bethanechol, arecoline, pilocarpine etc. are used.
Methacholine, carbachol, bethanechol are synthetic cholinomimetics where as arecoline, pilocarpine, muscarine are obtained from the natural sources; alkaloids.
Methacholine :
(CH3)3-N+-CH2-CH(CH3)-O-CO-CH3
Many cholinomimetics were discovered out of which few have pharmacological action.
In Ach, one -CH3 group is added, which resist hydrolysis of methacholine by chE. Thus, its action is prolonged than Ach. It has the effect on the muscarinic receptor. By intra-venous infusion of it produce hypotension & bradycardia.
Carbachol & Bethachol:
(CH3)3N+-CH2-CH2-O-CO-NH2 -carbachol
They are carbomyl esters which are completely resistant to hydrolysis. Carbachol have effect on nicotinic receptors and bethachol have action through muscarinic receptors.
(CH3)3N+-CH2-CH(CH3)-CO-NH2 -bethachol
They are only responsible for decrease in BP at low dose which affect GIT and urinary tract.
Pilocarpine:
It is obtained from the plants of pilocarpus genus. It is diaphoretic drug and also produces salivation. It also has effect on the pupil. So it is used in the open angle glaucoma. It is used to decrease intraocular pressure. It is also used in xerostomia.
Arecoline:
It is obtained from the seeds of betel nut. It acts at nicotinic receptors and it is euphoretic drug.
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