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Adrenergic Antagonists

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voguvidu's version from 2016-11-01 19:40

α blockers

Question Answer
What is the main effect of alpha antagonists? Side effects (2)?decrease peripheral resistance > BP ↓; can cause postural hypotension and reflex tachycardia
What is epinephrine reversal?give an α blocker and then give epinephrine > BP can actually go down because of beta-2 effect
What is the mechanism of reflex tachycardia?alpha block > BP lowered and alpha-2 blocked > CNS fires more NE on β1 receptors > HR increased
What type of agonist can prevent reflex tachycardia?α2 agonist > blocks release of NE from pre-synaptic nerves
What happens if you block α2?more NE released > more β1 stimulated > increase in rate and force of contractions (reflex tachycardia)
Action of α blockers on urinary?more urine flow: detrusor contracts and sphincters relax
Action of α blockers on men’s sexual function?block alpha receptors in prostate (and other spots) > decreased ejaculation > longer erection
4 indications for α blockers?pheochromocytoma, chronic HTN, urinary obstruction, ED
What is a pheochromocytoma? Sx? Rx?tumor of adrenal gland > way too much adrenaline; treat with phenxybenzamine/phentolamine
Why do Prazosin, Doxazosin, and Terazosin produce less reflex tachycardia than drugs like phentolamine?reflex tachycardia is a result of α2 autoreceptor NE blockage (and those drugs only block alpha-1)
What is BPH?benign prostatic hyperplasia
Which type of antagonist sometimes used in Raynauds?α1
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Graphs

Question Answer
Epinephrine’s effect on BP?
Phenylephrine’s effect on BP?
Epinephrine’s effect on BP after an α block? because will more predominantly affect β2 receptors in skeletal muscle
Phenylephrine’s effect on BP after an α block?modestly ↑ because it does not bind to β2 (α1 agonist)
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β blockers

Question Answer
By what two general mechanisms do β blockers treat HTN?decreasing cardiac output; inhibit release of renin (which increases BP)
Do what in the heart?depress SA and AV nodes; block β1 receptors; > negative chronotropic (rate) effect and negative inotropic (contractility) effect
Which blocker causes reflex vasoconstriction. Explain.β2; β2 receptors allow for vasodilation of skeletal muscle; block this > vasoconstriction of α1 is unopposed (skin and gut)
What is the life-threatening consequence of propranolol?blocks β2 receptors > can cause life threatening bronchoconstriction in asthmatics
Beta blockers do what to the eye?decrease secretion of aqueous humor
Overall effect of β blockers on glucose?blocks glycogen and glucagon breakdown > less glucose > hypoglycemia
Some β blockers have partial agonist activity and local anesthetic properties; describe these, selectivity, lipid solubility, half life, and bioavailability of timolol.timolol: no partial agonism, no anesthesia, moderate lipid solubilty, 4-5 hours; 50% bioavailbity; used to decrease amount of aqueous humor production
3 cardiac indications for β blockers?HTN, ischemic heart disease/MI (during and prophylactically), congestive heart failure,
3 other indications for β blockers?glaucoma, hyperthyroidism (thyroid storm), migraine
Other indications for propranolol?Rx for stage fright, postural (essential) tremors, Sx of alcohol withdrawal
What is the only thing that propranolol not used to treat for?heart failure
Propranolol, esmolol, and acebutol?attenuate supraventricular arrhythmias
Why are β blockers preferrable to cholinergic drugs to treat open-angle glaucoma?they do not affect pupil size or accomodation
Why is it important that timolol lacks MSA (membrane stabilizing activity – anesthesia)if it had it > could have corneal damage
What is ISA?intrinisic sympathomimetic activity – partial agonism
Contraindication?partial/complete AV block (depresses) > could stop heart beating
Why can they cause sexual impairment?block vasodilation
What is the difference between chronotropic and inotropic effects?chrono - rate; ino - contractility
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Drugs – α blockers

Question Answer
Prazosin, Doxazosin, and Terazosinreversible α1 blockers; HTN and urinary retention
Phenoxybenzamineirreversible α blocker (slightly prefers α1), pheochromocytoma
Phentolaminereversible α blocker (α1 = α2); HTN emergencies
Rauwolscinereversible α2 blocker
Rohimbinereversible α2 blocker
Tolazolinereversible non selective alpha blocker
Labetalolα and β blocker; used to treat HTN emergencies and pheochromocytoma
Carvedilolα and β blocker; used to treat HTN
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