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Date Submitted: 10/18/2013 11:11 AM
Muscarinic Cholinergic Agonists
Drug | Indication | General Info |
Acetylcholine | None | Nonselective actions on cholinergic receptors↓HR, ↓SV, ↓BP (when administered by injection; by acting on M3 receptors), ↑intestinal and bronchiolar secretionsDisadvantages: rapidly hydrolyzed and nonselective → many side effects |
Methacholine | Diagnostic: assess bronchiolar reactivity | Relatively selective for M receptorsCV effects if given IVBronchoconstrictor action |
Bethanechol | Atony of G-I-U smooth muscle (esp. postoperatively) | Selective for M receptorsNot hydrolyzed by aceylcholinesterase |
Carbachol | Rarely used – can be used for glaucoma (Lippincott’s) | Nonselective actions on both N and M receptorsLong-acting |
Muscarine | Not used as a drug | Naturally occurring in poisonous mushrooms |
Pilocarpine | Glaucoma (↓IOP)Xerostomia 2⁰ to Sjogren’s syndrome | Selective for M receptorsMiotic (constriction of the pupil): ↓IOP by acting on the circular muscleHas CV effectsNaturally occurring |
Cevimeline | Xerostomia | SyntheticSelective for M receptorsFewer CV effects than Pilocarpine |
* M-agonists increase: bronchospasm, GI cramps/diarrhea, miosis, sweating, urination, lacrimation, salivation, bradycardia (use caution in patients with asthma, ulcers or hypertension)
* M-agonists, when injected can cause vasodilation. Binding to endothelial cell M3 receptors can activate NO synthase which produces NO causing vasodilation.
* M1 receptors:
* Location: CNS neurons, ganglion cells near parietal cells of stomach
* Signalling: involves phospholipase C →IP3→Ca2+
* Application: Alzheimer’s Disease, ulcers (M1 antagonists used)
* M2 receptors:
* Location: heart, postganglionic nerve ending (i.e.- located on the presynaptic side), some smooth muscle
* Signalling: involves inhibition of adenylate cyclase and activation of K+ channels which allow K+ to enter and hyperpolarize the cell
* Application:...