Antihypertensives Flashcards
Define BP
The force/tension of blood pressing against arterial walls
What is the equation for BP?
CO x SVR
What is essential HTN?
no identifiable cause, likely d/t environment and genetics. 95% of cases.
What is secondary HTN?
CKD, Cushings, pheos, OSA
What are the limits for Stage 1 HTN?
130/80
What are the limits for Stage 2 HTN?
140+/90+
What constitutes HTN crisis?
180+/120+
What regulates BP?
Pressure sensitive neurons called baroreceptors in the aortic arch and carotid sinuses–they form the vagus nerve at the aortic arch
Explain mechanism of BP regulation.
If BP falls too low baroreceptors send signals to adrenal medulla causing release of catecholamines and increasing sympathetic activity through activation of beta and alpha receptors.
What do beta 1 receptors do?
increase HR and SV, thus increasing CO and BP
What do alpha 1 receptors do?
on smooth muscles, vasoconstrict, increasing vascular resistance and increasing BP
What are the classifications of antihypertensives?
sympatholytics, calcium channel blockers, angiotensin converting enzyme inhibitors, angiotensin II receptor inhibitors, centrally acting drugs, diuretics
What’s another name for sympatholytics?
adrenergic antagonists
What do sympatholytics do?
inhibit activity of SNS mediated by epi/NE, bind to adrenergic receptors of smooth muscle causing vasodilation and decreased SVR, prevent their activations.
What are the groups of sympatholytics?
alpha blocker and beta blocker
What are examples of non-selective alpha blockers?
phentolamine, phenoxybenzamine
How can non-selective alpha blockers cause tachycardia and arrhythmias?
non-selective bind to alpha-1 and 2, NE acts on alpha-2 so blocking this results in more NE release which can then stimulate beta-1 receptors on the heart
What’s the difference between phentolamine and phenoxybenzamine?
phentolamine is reversible, phenoxybenzamine is not.
What do alpha-1 antagonists end in? examples?
-osin, prazosin, terazosin, doxazosin, alfuzosin, tamulosin
How do alpha-1 antagonists work?
selectively and reversibly block alpha-1 receptors from vascular smooth muscle which reduces PVR and BP
Is there still baroreceptor involvement with alpha-1 antagonists?
yes, cause hypotension and tachycardia
Do alpha-1 antagonists have more or less side effects that non-selective alpha blockers?
less, since negative feedback inhibition through alpha-2 receptors is still working
What’s different about the alpha-1 antagonists: alfuzosin, silodosin, and tamulosin?
little effect on BP but more so for relieving enlarged prostate, increased activity of alpha-1 receptors in prostate, less alpha-1 in blood vessels.
What are side effects of alpha-1 antagonists?
orthostatic hypotension, headaches, nasal congestion, reflex tachy unlikely because selective antagonist doesn’t impact NE regulating effect of alpha-2 receptor
What is yohimbine?
selective alpha-2 blocker. found in dietary supplements for ED, used to reverse sedation in vet medicine.
What is phenoxybenzamine’s MOA?
irreversible, noncompetitive nonselective alpha antagonist: binds irreversibly to different site on receptor and changes the shape of the receptor so it can’t bind to catecholamines anymore. Only way out is to synthesize new adrenergic receptors (takes 24 hours)
What is phenoxybenzamine used for?
treat pheo, symptoms HTN, tachy, arrhythmias, start 7-10 days preop, slow onset
What is the MOA for phentolamine?
REVERSIBLE, competitive nonselective alpha antagonist: competes with catecholamines for the exact same binding site. lasts about 4 hours
What is phentolamine used for?
used to treat pheos, also prevents dermal necrosis after inadvertent extravasation of alpha receptor agonist, ED, HTN crisis
What are the classifications for beta blockers?
first gen: nonselective, 2nd gen: b-1 selective, 3rd gen: vasodilatory (non-selective and b-1 selective)
Which beta blockers have additional alpha blocking activity?
carvedilol, labetalol
Discuss beta-1 receptors (not blockers).
located in heart, increases HR and contractility, in kidneys: stimulate juxtaglomerular cells- to release renin–renin-angiotensin-aldosterone system increases sodium and water retention which increases BP.
Discuss beta-2 receptors
in smooth muscle cells, lungs (causes bronchodilation), GI (decreases motility), eye (maintains shape), liver (promotes glucagon release)
What’s the MOA of beta blockers?
competitive inhibitors of beta-adrenergic receptors that counter the effects of catecholamines which leads to decreased sympathetic effects on cardiac system
What are beta blockers used to treat?
HTN, HF, heart attacks, angina, glaucoma, keep ICP down
What are examples of first generation, non-selective beta blockers?
propranolol, pindolol, nadolol, sotalol, timolol, oxprendolol, penbotalol