CV Drugs- Adrenergic-receptor Antagonists Flashcards
alpha-adrenergic antagonists- MOA: binds
competitively or covalently with alpha receptors
alpha-adrenergic antagonists- MOA: prevent the effect of
catecholamines and other alpha agonists form entering with the alpha receptor
alpha-adrenergic antagonists- MOA: located in
the heart and peripheral vasculature
alpha-adrenergic antagonists- effects
- vasodilation (orthostatic hypotension)
- reflex tachycardia
- blocks inhibition of insulin secretion
alpha-adrenergic antagonists- side effects prevent use as
essential antihypertensives
alpha-adrenergic antagonists- if beta blockade is not present,
maximal cardiac stimulation is allowed
phentolamine (Regitine)- MOA
competitive binding
phentolamine (Regitine)- blockade is
nonselective, alpha 1 and alpha 2
phentolamine (Regitine)- effects: vasodilation- __ blockade and direct action on __
alpha1
vascular smooth muscle
phentolamine (Regitine)- cardiac effects
cardiac stimulation (increased HR and CO)
reflex and alpha 2 blockade (blocks negative feedback of NE)
phentolamine (Regitine)- side effects
- dysrhythmias
- angina
- hyperperistalsis
- abdominal pain
- diarrhea due to parasympathetic tone
phentolamine (Regitine)- uses
- acute HTN emergencies, pheochromocytoma
- accidental infiltration of a sympathomimetic (5-15 mg in 10ml)
phentolamine (Regitine)- onset
2 min
phentolamine (Regitine)- duration
10-15 min
phenoxybenzamine (Dibenzyline)- MOA
irreversible covalent binding to alpha-receptors
phenoxybenzamine (Dibenzyline)- blockade
nonselective, alpha1>alpha2
phenoxybenzamine (Dibenzyline)- effects: vasodilation
orthostatic hypotension exaggerated with hypovolemia, HTN
phenoxybenzamine (Dibenzyline)- effects: impariment of
compensatory vasoconstriction (lower BP with hypovolemia and vasodilation drugs like volatile agents)
phenoxybenzamine (Dibenzyline)- __ CO
increased
phenoxybenzamine (Dibenzyline)- very little change in
renal blood flow even with decreased BP
phenoxybenzamine (Dibenzyline)- prevents the inhibition of
insulin secretion
phenoxybenzamine (Dibenzyline)- causes pupil
constriction
phenoxybenzamine (Dibenzyline)- chronić use may cause
sedation
phenoxybenzamine (Dibenzyline)- __ congestion
nasal
phenoxybenzamine (Dibenzyline)- uses
- control BP in pheochromocytoma
- in trauma patients, used to reverse vasoconstriction (shock), only after volume replacement
- Raynaud’s syndrome
phenoxybenzamine (Dibenzyline)- onset
up to 60 min (IV)
phenoxybenzamine (Dibenzyline)- elimination 1/2 life
24 hours (duration can last up to 4 days)
prazosin (Minipress)- MOA
competitive, reversible binding with alpha receptors
prazosin (Minipress)- blockade
selective alpha 1 antagonist
prazosin (Minipress)- effects
- vasodilation of both arterioles and veins
- less reflex tachycardia (alpha 2 not blocked)
prazosin (Minipress)- uses
- HTN
- severe CHF
prazosin (Minipress)- onset
within 2 hours
prazosin (Minipress)- duration
10-24 hours
doxazosin (Cardura)- blockade
selective, alpha 1 antagonist
doxazosin (Cardura)- dose
once daily
doxazosin (Cardura)- peak
2-3 hours
doxazosin (Cardura)- elimination 1/2 life
22 hours
doxazosin (Cardura)- indications
- BPH
- HTN
beta-adrenergic antagonist- MOA: competitive binding to __ to block __
beta receptors
the effect of catecholamines and agonist on the heart and smooth muscles of airways and blood vessels
beta-adrenergic antagonists- prolonged or chronic use of beta blockers causes
up-regulation of beta receptors
classifications of beta-adrenergic antagonists
- nonselective
- cardioselective
- partial antagonist
- pure antagonist
nonselective beta-adrenergic antagonists block
both beta 1 and beta 2 (timolol and propranolol)
cardioselective beta-adrenergic antagonists block
beta 1 (metoprolol, atenolol, esmolol)
beta-adrenergic antagonists partial antagonists
intrinsic sympathomimetic effect (less myocardial depression and HR reduction)
beta-adrenergic antagonists put antagonist
no sympathomimetic effect
selectivity of beta-adrenergic antagonists is
dose-related; if a big enough dose of a carioselective beta-blocker is give, the effect can impact beta-2 receptors
beta 1 blockade removes
sympathetic stimulation to the heart
beta 1 blockade effects
- negative inotropic effects
- negative chronotropic effects
- negative dromotropic effects
- increased in lusitropy
- decrease in bathmotropy
beta 1 blockade negative inotropic effects
myocardial depression
beta 1 blockade negative chronotropic effects
slows HR, sinus rate
beta 1 blockade negative dromotropic effects
- slows the conduction of impulse through the AV node
- slows rate of phase 4 depolarization
beta 1 blockade increase in lusitropy effects
ventricular relaxation
beta 1 blockade decrease in bathmotrophy effects
reduced degreee of excitability
beta 2 blockade effects
- vasoconstriction
- unopposed alpha vasoconstriction can cause decreased LV ejection
- bronchoconstriction
- prevents glycogenolysis, blocks tachycardia related to hypoglycemia, alters fat metabolism (lipolysis)
- inhibits uptake of K into skeletal muscle cells (increased serum K)
effects of beta-adrenergic antagonists- additive __ with anesthetics
myocardial depressant effects but safe to continue
hal>iso
effects of beta-adrenergic antagonists- CNS
cross BBB- fatigue, lethargy, vivid dream, memory loss, depression
effects of beta-adrenergic antagonists- cross placenta so
fetal bradycardia, hypotension, hypoglycemia
effects of beta-adrenergic antagonists- GI
nausea, vomiting, diarrhea
effects of beta-adrenergic antagonists- chronic use
fever, rash, myopathy, alopecia, thrombocytopenia
contraindications to beta-blockade-
- AV heart block
- hypovolemia
- COPD
- diabetic
- PVD, Raynaud’s syndrome, alpha-adrenergic agonist
contraindications to beta-blockade- AV heart block
slowed conduction may be enhanced
contraindications to beta-blockade- hypovolemia
eliminates tachycardia that is compensating for decrease in volume
contraindications to beta-blockade- COPD
increased airway resistance (nonselective or high doses)
contraindications to beta-blockade- diabetic
mask signs of hypoglycemia (nonselective or high doses)