click below
click below
Normal Size Small Size show me how
Pharm Autonomic NS
Adrenergic Antagonists
Question | Answer |
---|---|
NONSELECTIVE ALPHA ANTAGONISTS | phentolamine[Regitine], phenoxybenzamine [Dibenzyline] |
approximate equal affinities for | postsynaptic alpha 1, presynaptic alpha 2 |
as a result of the blockade of the postsynaptic alpha 1 | lowered BP |
as a result of the blockade of presynaptic alpha 2 | reflex cardiac stimulation b/c the negative feedback inhibition of neurotransmitter release is being blocked |
not used for tx of HTN, but used in tx of | pheochromocytoma to prophylax against hypertensive crisis as a result of release of norepi from the tumor |
SELECTIVE ALPHA 1 ANTAGONISTS | doxazosin [Cardura], prazosin [Minipress], terazosin [Flomax], alfuzosin [Uroxatral], silodosin [Rapaflo] |
reversibly block the effects of catecholamines at the postsynaptic aplha 1 receptors in | vascular smooth muscle and in the smooth muscle of the bladder neck and prostate |
can be used to treat HTN and BPH | doxazosin [Cardura], prazosin [Minipress], terzosin [Hytrin] |
used to tx BPH only | tamsulosin [Flomax], alfuzosin [Uroxatral], silodosin [Rafapflo] |
pharmacodynamics: reversible block postsynaptic alpha 1 resulting in decreased | arterial and venous vasoconstriction, decrease in peripheral vascular resistance |
both supoine and standing BP are lowered with most pronounced affect on | diastolic BP |
alpha 1 receptors are densely located in the bladder neck and prostate galnd therefore | these drugs are able to reduce bladder outflow obstruction without afffecting bladder contractility |
all the azosin drugs are contraindicated in the presence of | volume depletion and CHF because of peripheral vasodilaton |
risk for a 'first dose' reaction within 30-90 minutes of | orthostatic hypotension, esp with terazosin |
alpha 1 adrenergic blockade | nasal congestion, blurred vision, dry mouth, constipation, impotence, and urinary frequency |
clinical use: hypertension | drug of choice for treating HTN in older men with BPH |
All drugs in this class also raise HDL levels and reduce | total cholesterol and triglycerides |
Doxazosin and terazosin also lower | LDL |
also enhance insulin sensitivity, cause regression of LVH and improve the activity of the fibrinolytic system making them useful for | pts with DM and HF |
usually must be used in combination therapy because of | troublesome adverse rxns in almost all patients. |
also used off label to facilitate the passage of kidney stones | Hytrin, Flomax, and Cardura |
Cardura may be used as monotherapy because | it is the least likely in class to produce postural hypotension and fluid retention |
leading cause of nonadherence is | ejaculatoion inhibition and impotence (Uroxatral has less problem with this) |