physio pharmacology midterm Flashcards
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Hemicholinium
Prevents choline reuptake
Sildenafil
Viagra! Blocks cGMP phosphodiesterase from breaking down cGMP to 3,5’ GMP -> prolonged relaxation of BVs for erection
Vesamicol
Prevents vesicular storage of ACh
Botulinum toxin
Degrades synaptobrevin (SNARE) and prevents vesicle fusion/exocytosis. Clinically in cases with increased skeletal muscle tone, Lambert-Eaton syndrome, focal dystonias
AChE inhibitors
Elevate synaptic concentrations of ACh, therefore enhancing the postsynaptic effects of ACh (parasympathomimetics)
Edrophonium
AChE inhibitor/anticholinesterase. Simple alcohol. Short duration of action. Useful for dx’ing myasthenia gravis and Lambert-Eaton syndrome
Neostigmine and physostigmine
AChE inhibitor/anticholinesterase. Carbamic acid derivatives. Longer duration of action. Useful for tx’ing MG; reversal of neuromuscular blockers. (Physostigmine crosses BBB - good for CNS eg atropine poisoning.) Hydrolyzed by AChE so that covalent bond forms increasing half life of AChE inhibition
Parathion
AChE inhibitor/anticholinesterase. Organophosphate. Irreversible, toxic, commonly used in pesticides. Hydrolyzed by AChE to form an extremely stable complex. Only new recs can facilitate AChR activity and that can take weeks
Myasthenia Gravis
Autoimmune dz against Nm subtype (rec internalized), reduces NMJ transmission
Lambert-Eaton syndrome
Autoimmune dz against presynaptic Ca2+ channels. Reduces ACh release. Also used in dx
AChE inhibitor uses
- Increase neuromuscular transmission - MG, LE syndrome
- Increase parasympathetic tone (parasympathomimetic) - decrease glaucoma pressure via increased aq humor outflow, increase GI tract motility
- Increase central cholinergic neurotransmission in dementia (rivastigmine). Must titrate. Drugs delay development of cognitive and fxn’l impairment by 6 months.
- Reversal of paralysis from non-depolarizing neuromuscular blockers - increase ACh levels reverse the competitive block from these blockers
Negative SE’s of AChE inhibitors
- Excessive muscarinic stim - salivation, lacrimation, miosis, diarrhea, brachycardia
- Excessive nicotinic stim - muscle wkness and paralysis
- Chemical warfare - used as nerve gases - sx’s include mm wkness and paralysis
Dz using muscarinic agonists as txt: eye; GIT, bladder, urinary tract; salivary glands
Eye: glaucoma - contract circular m -> miosis -> aq humor outflow -> decreased intraocular pressure
GIT, bladder, urinary tract: restore GIT and UT motility after anesthesia/surgery
Salivary glands: xerostemia - increase salivation
Rivastigmine
AChE inhibitor. Improve dementia and Alzheimer’s dz cognitive sx’s. Requires titration phase. Drugs delay development of cognitive and fxn’l impairment by six months
Carbachol
MR agonist. Derivative of ACh. Differs in pharmacokinetic properties, resistance to ChEsterase and its affinity to both Nm and musc recs. Can’t be used systemically because of overall effects
Pilocarpine
MR agonist. Alkaloid similar to muscarine. Until recently the only alkaloid MR agonist to be used clinically. Used to tx dry mouth in Sjogrens syndrome
Methacholine
MR agonist. 3x more resistant to hydrolysis by AChE. Little affinity for nicotinic recs. used to dx asthma. Asthmatics are more sens to bronchial secreting actions of methacholine
Bethanecol
MR agonist. Almost completely selective for muscarinic recs. Choice drug for promoting GI and urinary tract motility. Particularly post-op, post-partum, and drug-related urine retention
Parasympatholytics
MR antagonists. Bind MRs and prevent ACh from exerting its effects. Competitive antagonists. Allow sympathetic responses to predominate.
Parasympatholytic prototype
Atropine. Actions: pupil dilation, tachycardia, decreased secretions (salivary, bronchial, GIT). Sympathetic response by antagonizing the parasympathetic
Clinical uses of atropine
- Produce mydriasis for opthalmological exam (applied topically)
- Reverse sinus brachycardia caused by excessive vagal tone
- Inhibit excessive salivation and mucus secretion during anesthesia and surgery
- Counteract the effects of muscarine poisoning AND poisoning with anticholinesterases
Scopolamine
MR antagonist. Significant CNS. Txt of nausea and motion sickness, intestinal cramp. As a general depressant and adjunct to narcotic painkillers. Truth drug in 50s and 60s
Pirenzepine
MR antagonist. Txt of peptic ulcers, an alternative to H2 histamine rec antagonists
Ipratropium
MR antagonist. Relatively selective for M3. Reduces bronchial secretions - used in COPD. Used in asthma where the bronchoconstrictive component is mediated by increased cholinergic neural tone