Alpha blockers Flashcards
Alpha 2A locations:
medulla (presynpactic)
Alpha 2A stimulation results in:
decreased sympathetic outflow
Alpha 2B locations:
vascular smooth muscle
Alpha 2B stimulation results in:
vasoconstriction
Mechanism of action of Clonidine
ALPHA 2 AGONIST
activation of central presynaptic alpha 2A receptors –> suppression of central symp. outflow
suppression of peripheral presynaptic alpha 2 receptors –> inhibition of NE, ATP, NPY release
Effects of Clonidine?
CNS - decreases BP (HR, SV decrease and relaxation of capacitance vessels)
Renal - decreases renin (alpha 2 stimulation)
Eyes - decreases IOP
Abrupt discontinuation of clonidine after high dosage prolonged use can result in
hypertensive crisis
Major therapeutic use of clonidine?
Minor?
Major: hypertension
Minor: decrease diarrhea in diabetics with autonomic neuropathy;
treatment of withdrawal of opiate addicts (their bp may increase);
menopausal hot flashes
MoA of methyldopa?
ALPHA 2 AGONIST
a-methylnorepinephrine (metabolite) stimulates alpha 2 receptors in brainstem
Effects of methyldopa?
CVS - decreases PVR. (little change in CO and HR)
renal system - decreases renin secretion (alpha 2)
Most common side effect of methyldopa?
sedation.
Also, dry mouth.
Which adrenergic drug causes a positive Coombs test?
methyldopa
Which alpha 2 agonist is used to decrease IOP?
apraclonidine
brimonidine
Which alpha 2 agonist is used as a muscle relaxant for treatment of spasticity?
Tizanidine
Which alpha 2 agonist is used as an anti-MI drug
Mivazerol
Which alpha 2 agonist is used to treat HTN AND ADHD in 16-17 year olds
Guanfacine
Result of alpha 1 blockage:
Beta 2 unopposed - vasodilation and decrease of PVR and BP
Result of alpha 2 blockage
presynaptic –> inhibition of inhibition of NE –> INCREASES NE –> B1 in heart and JG cells stimulated –> INCREASED HR and renin release
Alpha blocker used as diagnostic test for pheochromocytoma?
phentolamine
Major adverse affect of phentolamine
hypotension (can result in reflex tachycardia)
Alpha antagonist with 100x greater selectivity for alpha 1 over alpha 2. Used in pheochromocytoma
phenoxybenzamine
What used to treat HTN crisis following clonidine withdrawal?
phentolamine
What general drug class is used to treat pseudo-obstruction of the bowels
alpha blocker
What is used to treat dermal necrosis?
phentolamine
What is used to treat Raynaud’s phenomenon
PBZ or prazosin (CCB preferred)
List 5 selective alpha 1 blockers
Prazosin Terasozin Doxazosin Tamsulosin Alfuzosin
Which drugs have alpha 1ABD selectivity?
Prazosin, terazosin, doxazosin
Which drugs have alpha 1A selectivity
Tamsulosin, alfuzosin
Alpha 1A found in
prostate, bladder neck
Alpha 1B found in
blood vessels
Which selective alpha 1 blocker is not a quinazoline?
Tamsulosin
Which selective alpha 1 blockers induce apoptosis in prostate
terazosin, doxazosin
Which selective alpha 1 blockers treat only BPH and not HTN?
Tamsulosin, alfuzosin
Which selective alpha 1 blocker is used in SHORT term treatment of CHF?
Prazosin
Which selective alpha 1 blockers are more prone to the first-dose effect?
Prazosin, terazosin, doxazosin
Alpha 1 blockers dilate or constrict blood vessels?
Dilate
Selective alpha 2 blocker sold as dietary supplement.
Yohimbine (increases BP/HR, produces tremors)
Which ergot alkaloids are used in uterine atony postpartum/postpartum hemorrhage?
ergonovine/methylergonovine (causes uterine contraction)
Which ergot alkaloid is used in migraines?
ergotamine/dihydroergotamine
What is cafergot?
ergot alkaloid + caffeine to facilitate absorption
Which ergot alkaloids decrease prolactin secretion?
cabergoline, bromocriptine (high selectivity for pituitary dopamine receptors)
Which ergot alkaloid is used in senile cerebral insufficiency?
dihydroergotoxine
Which ergot alkaloid is used in parkinsonism?
Bromocriptine (as a dopamine agonist)
Prolonged vasospasm caused by ergotamine or ergonovine can result in:
gangrene
Imidazoline agonist, anti-hypertensive.
Acts on rostral ventro-lateral pressor and ventromedial depressor areas of the medulla oblongata.
Moxonidine
Rilmenidine
Difference between brimonidine and aproclonidine?
Brimonidine crosses BBB, but not apraclonidine
The only alpha 2 antagonist studied
yohimbine
