Lecture 16 - Adrenergic blocking agents Flashcards
What are the alpha-receptor blockers? (two)
Phentolamine
Phenoxybenzamine
What are the Alpha1 blockers? (one)
Prazosin
What is the alpha2 blocker?
Yohimbine
What are the beta blockers? (three)
Propranolol
Timolol
Sotalol
What are the beta1 blockers?
Metoprolol
Atenolol
What is the general distribution of alpha receptors?
Blood vessels
What does alpha 1 cause?
Mydriasis
Vasoconstriction
Contraction of genitourinary muscle
Ejaculation
What does alpha2 cause?
decrease NE release
Suppress insulin secretion
What does alpha blockade do you cardiovascular system?
Decrease peripheral resistance = Decrease D pressure
= decrease BP
Decrease venous return = othrostatic hypotension
What does alpha blockade do to the eyes?
Miosis (via lack of radial muscle stimulation)
What happens to the nasal passages with alpha blockade?
Nasal congestion due to decreased vasoconstriction
What happens to urinary flow with alpha blockade?
urine flow increases
Base of bladder + urinary sphincter + prostate relax
What happens to sexual reproduction with alpha blockade?
Ejaculation inhibited
What do alpha2 blocking agents do?
Increase NE release
What is the basic distribution of beta receptors?
Heart
What does the B1 receptor do? (two things)
Increase heart rate and force
Increase renin secretion
What does B2 stimulation cause? (four things)
Relax bronchioles
Dilate BV supplying skeletal muscles
Increase glycogenolysis
Increase aqueous humor + intraocular pressure
What does B2 stimulation cause?
Lipolysis
What are the basic three things that occur with beta blockade in the heart and kidney ?
Decrease in HR and force
Decrease in CO and O2 demand
Decrease in renin secretion
What will happen overtime with beta blockade?
Decrease in BP in patients with hypertension
What does beta blockade cause with metabolism?
Decrease glycogenolysis + lipolysis
What is the behavior of a competitive antagonist?
If enough agonist is present can reach Emax
What is the behavior of a non-competitive antagonist?
Emax is lowered, no matter the concentration of the agonist
What are the competitive, reversible alpha antagonists?
Phentolamine + Prazosin
What is the irreversible, non-competitive alpha antagonists?
Phenyoxybenzamine
What are the six major things that occur with alpha blockade?
Reduced vasoconstriction Reflex tachycardia Miosis Nasal stuffiness Decreased resistance to urinary flow Inhibition of ejaculation
What occurs once vasoconstriction is reversed with an alpha blocker?
Baroreceptors sense decrease in BP and increase SNS output
Why does reflex tachycardia occur with an alpha blocker?
Decreased BP
Stimulates baroreceptors = increase NE release
NE –> Beta = Increased HR
What happens when you block the alpha effects of epinephrine?
Drop in BP due to lack of vasocontriction
Heart rate increase
What receptors does phentolamine target?
Alphas
What does phentolamine do?
Decrease diastolic BP + Peripheral resistance
Reflex tachycardia
What are the side effects of phentolamine?
Tachycardia + Arrythmia + Myocardial ischemia + Hypotension
When is phentolamine used?
Hypertensive crisis from pheochromocytoma or MAO inhibitors
Prevents necrosis after accidental injection of alpha agonist
What are the side effects of phenoxybenzamine?
Postural hypotension + Tachycardia
Nasal congestion + no ejaculation
When is phenoxybenzamine used?
NE/EPI levels are too high and can overcome the effects of a drug that was a competitive agonist
When is phenoxybenzamine used?
Small animals with detrusor areflexia
What is a pheochromocytoma?
Adrenal neoplams that secretes NE/EPI
What is the treatment of a pheochromocytoma?
treat with phenoxybenzamine then surgery
What is a sign there is a pheochromocytoma?
Sudden onset of severe hypertension + tachycardia + arrhythmia
What do you test for in the urine to see if a pheochromocytoma is a possibility?
VMA
What does prazosin target?
Alpha 1
What does prazosin do?
Relax arterial + venous SM = decreased peripheral resistance
Decrease venous return = decrease preload
What is an upside to using prazosin?
no alpha2 so less tachycardia
What are side effects of prazosin?
Dizziness + Lethargy
When is prazosin used?
CHF
Functional urethral obstruction
What does yohimbine target?
Alpha2
What does Yohimbine do?
Increase NE release = increase BP and HR
Increased motor activity
What is a side effect of yohimbine?
tremors
What can yohimbine be used for in animals?
Reverse effects of xylazine
What does beta blockade cause in the lungs?
Bronchoconstriction
Where should you never use a beta blocker?
Horses with RAO
What does a B blocker do in the eye?
Decrease formation or aqueous humor
What does chronic use of a beta blocker do in regards to metabolism?
increase VLDL + decrease HDL
What beta blockers have the ability to be a local anesthetic?
Proranolol + Metoprolol
How does metoprolol + propranolol have local anesthetic capabilities?
Membrane stabilizing via sodium channel blockade
What are the effects of propranolol?
Decrease HR + Contractility
Decrease renin + lipolysis + glycogenolysis
What are the pharmokinetic characteristics of propranolol?
Low bioavalibility
Lipid soluble = CNS activity = sedation
What is the major side effect of propranolol?
Bronchoconstriction
What is another medication similar to proprananol?
Timolol
How does timolol differ from proprananol?
No local anesthetic affect
= can be used in eye
What other symptoms are seen with proprananol use?
Bradycardia Increase symptoms seen with CHF Lethargy Decrease excercise tolerance (B2 blockade, muscles sad) Increase glucose levels
What happens with abrupt discontinuation of propranaol
Tachycardia + Arrhythmia
What are your two Beta1 selective blockers?
Metoprolol + Atenolol
What is the effect of metoprolol + atenolol?
Heart mostly Decrease HR + Contractility Decreased O2 demand Decreased renin secretion = DECREASE BP
What is metoprolol + atenolol used for?
Hypertension + Tachycardia + Arrhythmia
