Adrenergic Antagonists Flashcards
effects of binding alpha1 receptors
contraction of arterial, venous and visceral smooth muscle
effects of binding alpha2 receptors
suppression of sympathetic output, increased vagal tone, platelet aggregation, inhibition of the release of NE and ACh fron nerve endings, regulation of metabolic effects.
what are the effects on alpha-AR antagonists?
decreased BP by relaxation of arteriolar and venous tone which decrease peripheral vascular resistance
reverses the vasopressor effects of epinephrine - epinephrine reversal
relieves urinary symptoms of BPH by blockade of alpha1 AP
what are some reasons to use the epinephrine reversal phenomenon?
.
what are the adverse effects of alpha AR antagonists?
orthostatic hypertension - prevention of venoconstriction
reflex tachycardia
sedation, depression, miosis, nasal stuffiness, increase GI tract motility and diarrhea, and impaired retention
what type of drugs interact with alpha-AR antagonists?
peressors
phosphodiesterase-5 inhibitors: potentiates the effect causing hypotensive
alpha-adrenergic receptor antagonists - enhances hypotensive effects of other antihypertensive drugs.
combinations of antihypertensive drugs with different MOA are used to manage BP
what are the non-selective alphaAR antagonists?
phenoxybenzamine
phentolamine
phenoxybenzamine
irreversible alpha-adrenergic antagonist
used preoperatively for pheochromocytoma and urinary retention
phentolamine
competitive nonselective alpha-adrenergic antagonist
effect - brief antagonism of circulating Epi and NE
uses:
diagnosis of pheochromocytoma
control BP in patients undergoing surgery for pheochromocytoma, reversal of the extravasation of Epi, NE, dopamine and phenylephrine, reversal of dental anesthesia (any one that has a vasoconstrictor)
selective alpha1 R antagonists
Prazosin
Terazosin
Doxazosin
alfuzosin
tamsulosin
silodosin
therapeutic uses and effects of selective alpha1 AR antagonists
potency is similar among alpha1 R subtypes
used for hypertension - relaxes arerial and venous smooth muscel which decreases TPR and pre/afterload
benign prostatic hyperplasia
relax smooth muscle in bladder neck and prostate improving urine flow
adverse effects of selective alpha1 AR antagonists?
exhibits a first dose effect of orthostatic hypotension -> common cause of falls - palpitations, tachy, dizziness, light-headedness and syncope
intraoperative floppy iris syndrome during cataract surgery
rare - priapism
Prazosin
alpha 1 receptor blocker - Quinazoline
given oral with 50-70% bioav, binds plasma proteins, hepatic metabolism, fecal excretion, 2-3 x daily dosing
Relax both arterial and venous vascular smooth muscle decreases peripheral vascular re-
sistance and venous return to the heart leading to a decreased cardiac preload and afterload
used for hypertension and BPH
orthrostatic hypotension
tamsulosin
relatively selective alpha1 receptor antagonist - treatment of BPH
first dose effect occurs less commonly with this drug
can cause abnormal ejaculation
Intraoperative floppy iris
syndrome
contraindicated in pts with sulfonamide allergy due to ignorance
Yohimbine
from yohimbe bark
competitive alpha2 AR antagonist
increases blood pressure and heart rate
enhances motor activity - tremors
secual stimulant, mood stimulant
yohimbine adverse effects
tachycardia and hypertension
nausea, vomiting, anorexia, salivation
tremors, diaphoresis
headache, agitation, anxiety and irritability
remember alpha2 is a G-inhibitory PCR, decreasing it’s activity increases sympathetic surge.
types of beta blockers
classic nonselective beta blockers
beta1 selective
nonselective beta blockers with additional actions
selective beta1 blockers with additional actions
what are the additional actions associated with some nonselective and selective beta blockers?
Additional actions include α
ARs block, β oxide (NO) production, block Ca2+ entry, open K+ channels, or possess antioxidant properties; these additional properties may offer therapeutic
advantages
how do beta blockers modulate epinephrines effects?
blood pressure still increases because vasoconstriction functions have not been blocked (alpha1 R effect)
HR and cardiac contractile force are not increased because the beta blocker blocked epi from binding beta R
therapeutic uses of beta blockers
hypertension
ischemic heart disease
myocardial infarction
congestive heart failure
arrythmias
glaucoma
hyperthyroidism (disease causes excess beta R on heart)
Pheochromocytoma - alpha blockers needed as well
portal hypertension
migraines
situational anxiety
adverse effects of beta blockers
bradycardia, insomnia, fatigue, depression, bronchospasm (COPD, asthma pts), sexual dysfunctions
crosses placenta
what happens with abrupt discontinuation of beta blockers?
abrupt discontinuation of beta blockers can cause a drastic increase in BP and can cause severe angina, myocardial
infarction or ventricular
arrhythmia, and may
increase the risk of sudden
death.
-body upregs receptors during course of drug treatment
what relationship is seen between beta blocker and diabetes mellitus patients?
beta blockers can hide the warning symptoms of hypoglycemia and inhibits reflex hepatic production of glucose
hypoglycemia can be very serious
what drugs do beta blockers interact with?
decreases absorption of chelators
CYP inducers or inhibitors
calcium channel blockers
other antihypertensives
NSAIDS
propranolol
lipophilic and enters CNS
given orally with an extensive first pass effect
affinity for beta 1 and 2 R
used for angina, MI, arrhythmias, pheochromocytoma;
thyrotoxicosis; prophylaxis of migraine; parkinsonian tremors;
prophylaxis of esophageal variceal hemorrhage; others
