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CholinergicDrugs
lecture 7-8 & 10 sternweis
| Question | Answer |
|---|---|
| hemicholinium | used only in lab setting, selectively blocks choline transport into nerve (thus no ACh can be made) |
| alpha-latrotoxin | from black widow spider, causes constitutive release of ACh from vesicles at cholinergic junctions |
| botulinum toxin A | cleaves proteins required for exocytosis, effectively inhibiting release of ACh from vesicles at cholinergic junctions |
| tetanotoxin | blocks release of ACh from inhibitory neurons, causes tetanus |
| physostigmine | reversible AChE inhibitor |
| organic phosphates like DFP (used in insecticides and chemical warfare) | irreversible AChE inhibitor |
| nicotinic cholingergic receptor: type of channel, number of subunits, result of stimulation | ligand-gated ion channel; 5 subunits (2 alpha one beta, delta & gamma); influx of Na & Ca --> depolarization |
| hexamethonium | preferentially blocks ganglionic nicotinic receptors (autonomic ganglia and adrenal medulla) |
| decamethonium | preferentially blocks somatic neuromuscular nicotinic receptors |
| muscarinic receptors are used to modulate intrinsic organ activity using slower, graded responses | |
| atropine | competitive inhibitor of muscarinic receptors, tertiary amine with penetration into CNS, used for cholinergic excess or PALS/ACLS |
| Tertiary amine comp'ds have greater effects in CNS than quaternary amines | |
| LOW dose ACh stimulates muscarinic receptors and HIGH dose ACh stimulates both muscarinic and nicotinic receptors | |
| bethanechol | strictly muscarinic agonist (oral or SQ only), resists degradation by BChE and AChE but provides additive effect to endogenous ACh, used for intestinal atony and bladder retention or dx'ing atropine toxicity |
| contraindications for muscarinic agonists | asthma - bronchoconstricts hypothyroidism, coronary insuff - hypotension PUD, physical obstruction - gastric secretion, increased GI motility |
| antidote for muscarine overdose | atropine |
| pilocarpine | tert. amine muscarinic agonist with effects in CNS, potent diaphoretic (sweat test for CF), used for xerostomia and Sjogren's syndrome |
| tropicamide | muscarinic antagonist with short half-life (good for eye exams) |
| tolterodine | [Detrol] muscarinic antagonist, specificity for M3, used for urinary incontinence |
| ipratropium | [Atrovent] muscarinic antagonist, selective penetrance with local administration |
| best tx for acute COPD/asthma attack | anticholinergic with beta2 agonist |
| signs of anticholinergic intoxication and preferred tx | cutaneous vasodilation, anhidrosis and hyperthermia, nonreactive mydriasis, delirium and hallucinations, urinary retention tx: ACheE inhibitor - physostigmine, maybe diazepam for antipsychosis |
| donepezil | [Aricept] AChE inhibitor - competitive antagonist (reversible by flooding with ligand), tertiary amine with CNS effects |
| physostigmine | carbamoylating AChE inhibitor (slowly reversible with hydrolysis), tertiary amine with CNS effects, used for myasthenia gravis or acute narrow angle glaucoma |
| neostigmine | carbamoylating AChE inhibitor (slowly reversible with hydrolysis), quaternary amine with selective effects at the NMJ, used to treat paralytic ileus or bladder atony |
| sarin | type of irreversible AChE inhibitor |
| danger of using antimuscarinic for mydriasis | precipitating an acute narrow angle glaucoma attack as iris squishing up closes off uveoscleral outflow |
| effect of AChE inhibitor will be initial facilitation then inhibition at all sites EXCEPT muscarinic receptors where it's always stimulatory | |
| signs of cholinergic excess or intoxication | S - salivation L - lacrimation U - urination D - diaphoresis G - GI evacuation E - emesis |
| pralidoxime | AChE reviver, only effective if used early and after phosphorylating AChE inhibiting agents (NOT effective after physostigmine or neostigmine) |
| effects of nicotine at low and high doses | low - most prominent is excitation of resp, after repeated use increased HR and BP high - affects all nicotinic receptors even in CNS = sharpening of attn, dependence toxic - stimulation then depression of resp muscles |
| trimethaphan | quaternary sulfonium that inhibits ganglionic nicotinic receptors = withdrawal of all autonomic tone, used only in emergencies like hypertensive crisis in pt with dissecting aortic aneurysm |
| d-tubocurarine and vecuronium | non-depolarizing competitive inhibitors of NMJ nicotinic receptors, good for conscious sedations b/c they have little effect on diaphragm or CNS, known side effects: histamine release. caution if myasthenia gravis pt taking AChE inhibitor |
| succinycholine | depolarizing nicotinic NMJ agonist, used for short procedures, 1st initial activation then desensitization causes receptor blockage and flaccid paralysis, little CNS effect, potential for K+ loss from muscles, quickly hydrolyzed by plasma cholinesterase |
| caution with these diseases if giving succ | genetic plasma cholinesterase deficiency (will prolong paralysis, possibly cause apnea) malignant hyperthermia (when used with halothane causes rapid efflux of Ca++ from muscle b/c of defective RyR) |
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sirprakes
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