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Cholinergic Drugs
USMLE Step 1
Drug | MOA & ADRs |
---|---|
Nicotinic | (ligand gated ion channels), SNS & PNS ganglia-Type 1 sites, skeletal muscle-Type 2 sites |
Muscarinic | M1: ANS ganglia, brain, gastric parietal, vascular smooth muscle, M2: heart, M3: glands & bronchial smooth muscle, M4: CNS, M5: CNS; M1, 3, & 5 + PLC = Ca influx; M2 & 4 - adenylate cyclase = K out & Na in |
Bethanechol | MOA: direct cholinergic used for atonic bladder, i.e. postpartum to increase bladder tonicity; ADRs: diaphoresis, flushing, increased urinary urgency, nausea & diarrhea |
Pilocarpine | MOA: direct cholinergic used via eyedrops for acute angle glaucoma, decreases accommodation, most potent + of glandular secretion if used systemically; ADRs: diaphoresis, flushing, increased urinary urgency, nausea & diarrhea |
Carbachol | MOA: direct cholinergic only used via eyedrops for glaucoma, very long duration w/ very high potency; ADRs: diaphoresis, flushing, increased urinary urgency, nausea & diarrhea |
Physostigmine | MOA: AChEI used in the tx of myasthenia gravis, increased GI & bladder motility, also used to tx overdose w/ TCAs & atropine |
Neostigmine | MOA: AChEI used in the tx of myasthenia gravis, increased GI & bladder motility; ADRs: spastic paralysis |
Edrophonium | MOA: AChEI shorter onset & duration of action than neostigmine, used to dx myasthenia gravis that will give relief of sxs; ADRs: cholinergic crisis; *Note antidote is atropine* |
Organophosphates | MOA: AChEI used in the tx of closed angle glaucoma due to strong miotic effect, otherwise used for insecticides & nerve gas; *Note antidote is atropine or pralidoxime (2-PAM)* |
Atropine MOA: | antimuscarinic, a belladonna alkaloid, works centrally & peripherally, use 4 reverse bradycardia & reduce hyperactive bladder, incurs mydriasis-inability focus 4 near vision |
Scopolamine | MOA: antimuscarinic drug that is a belladonna alkaloid, >er CNS effect than peripheral effect, duration is >er than that w/ atropine, most effective 4 motion sickness; ADRs: block short term memory, low dose include sedation, high dose causes excitement |
Atropine ADRs | urinary retention, xerostomia, blurred vision, 'sandy' eyes, tachycardia, constipation, confusion & glaucoma attack |
Tubocurarine | MOA: antinicotinic, nondepolarizing, competitive blocker, affects the small, rapid muscles 1st, then lrger ones & finally the diaphragm; *Note antidote neostigmine or edrophonium depend on degree of overdose &/or sxs* |
Pancuronium | MOA: antinicotinic, nondepolarizing drug causes less histamine release than tubocurarine-so more favorable side effect profile; ADRs: vagolysis w/ resultant dangerous tachycardia |
Succinylcholine MOA: | antinicotinic, depolarizing blocker acts like ACh binding @ receptors-persists there, initial cause fasciculations then flaccid paralysis, use 4 rapid endotracheal intubation, electroconvulsive shock tx & surgery |
Succinylcholine ADRs | significant apnea, malignany hyperthermia if used in combination w/ anesthetic agent called halothane (occurs in genetically susceptible ppl) & tx is dantrolene that - Ca release from sarcoplasmic reticulum |
Antinicotinic drugs ADRs | note that exercise caution when using drugs such as halothane, aminoglycosides (- ACh release) & Ca channel blockers that enhance neuromuscular block |