Alpha-Blockers Flashcards
Prazosin
Prazosin
Alpha 1 selective antagonist
Binds to alpha 1 adrenergic receptors and blocks the actions of catecholamines, preventing the GPCR cascade and resulting in vasodilation with MINIMAL reflex tachycardia. Leads to vasodilation, decrease SVR, decrease BP. Minimal tachycardia r/t alpha 2 activity as it is a selective agent. Used to tx pheochromacytoma, raynaud’s, and BPH.
Pk:
Onset: 1 hour - PRODRUG
DOA: 6-10 hours
E1/2T: 2-4 hours
PB: high
Metabolized by liver and excreted in BILE and FECES
DOSE:
1 mg PO at bedtime
SE:
Dizziness
HA
Orthostatic hypotension
EDEMA
ANTI-CHOLINERGIC EFFECTS - dry mouth, urinary frequency
Hepatoxicity
SLE
C/I:
Caution with REGIONAL - r/t decrease in BP
hypovolemia/hypotension
caution with BETA BLOCKERs
Caution with other anti-HTN
C/I IN pregnancy
Phenoxybenzamine
Phenoxybenzamine
Non selective, non-comepetive alpha antagonist, more active at alpha 1 than alpha 2
COVALENTLY binds to alpha 1 and alpha 2 receptors, prevents action of catecholamines and GPCR cascade and leads to vasodilation, decrease SVR, decrease BP, and also with phenoxybenzamine reflex tachycardia. Used to tx pheochromacytoma or raynaud’s
Pk:
Onset 1 hour - prodrug
e1/2T: 24 hours
Eliminated in liver and excreted in BILE and FECES
Dose:
10-120 mg/day PO
SE:
Reflex tachycardia
orthostatic hypotensoin
nasal congestion
impotence
c/I:
Severe hypovolemia, hypotension
treat hypotension with NE over EPI
Phentolamine
Phentolamine
Non selective alpha antagonist
Blocks alpha 1 and alpha 2 and prevents the actions of catecholamines and GPCR cascade. Induces vasodilation, decreases SVR, decreases BP, leads to hypotension and alpha reflex tachycardia. Used to treat HTN crisis like in pheochromacytoma, also with infiltration of vasopressor agents into skin.
Pk:
onset: 2 minutes!
DOA: 10-15 minutes
E1/2t: 19 minutes
Liver metabolism and excreted 10% unchanged in urine.
Dose:
1-5 mg IV bolus
SE:
Reflex tachycardia
angina
MI
Arrthymias
HA
cramping/diarrhea
