Alpha and Beta Adrenergic Blockers - LeBlanc Flashcards
Catecholamines causes peripheral (inhibition/excitation) on gut, bronchial, blood vessles supplying skeletal muscle SM
inhibitory
What are the effects on the heart of catecholamines?
increase in frequency and contractile force, increase conduction velocity
Regarding metabolism, what are the effects of catecholamines on fats and sugars?
glycogenolysis from liver and skeletal muscles
release of free fatty acids from adipose tissue
Which endocrine hormones do catecholamines regulate?
insulin
renin
pituitary hormones
What are the CNS effects of catecholamines?
wakefulness
appetite
resp. stim
psychomotor activity
What are the PREjunctional actions of catecholamines?
inhibition or facilitation of neurotransmitter release
describe the strength of Epi, NorEpi, and Iso on a1 receptors
Epi > NE»_space; Iso
phenylephrine
describe the strength of Epi, NorEpi, and Iso on a2 receptors
Epi > NE»Iso
clonidine
describe the strength of Epi, NorEpi, and Iso on B1 receptors
Iso > Epi =NE
dobutamine
describe the strength of Epi, NorEpi, and Iso on B2 receptors
Iso > Epi»_space; NE
terbutaline
describe the strength of Epi, NorEpi, and Iso on B3 receptors?
Iso = NE > epi
Wat is the a1 antagonist?
prazosin
What is the a2 antagonist?
yohimbine
What is the B1 antagonist?
metoprolol
which two receptors are found on smooth muscle?
a1
B2
which receptor is found on nerve terminals?
a2
Which receptor is found on cardiac muscle?
b1
which receptor is found on adipose tissue?
B3
What is the effect of stimulating a1 receptors?
contraction of SM
what is the effect of stimulating a2 receptors?
decreased transmitter release
wha is the effect of stimulating B1 receptors?
increase:
chronotropic
inotropic
dromotropic
What is the effect of stimulating b2 receptors?
SM relaxation (think albuterol inhalers)
what is the effect of stimulating b3 receptors?
lipolysis
what is the G protein assc’d with a1?
Gq
what is the G protein assc’d with a2?
Gi/o
what is the G protein assc’d with B receptors?
Gs
a1 directly stimulates (blank), which activates (blank) which converts PIP2 to IP3 and DAG
phospholipase
Protein kinase C
IP3 production allows for (blank) release from intracelllular stores which causes SM contraction
Ca
a2 stimulation blocks (blank) release from intracellular stores which blocks neurotransmitter release
Ca
A2 activation blocks (blank) activity which converts ATP to cAMP
adenylyl cyclase
cAMP production post A2 signaling has what effect on SM?
contraction
B receptors activate adenylyl cyclase to produce cAMP which does what?
increase cardiac contractility
SM relaxation
glycogenolysis
How does calcium release from intracellular stores actually get the cell to do things?
activates Ca dependent protein kinase
which two receptors have competing action on adenylate cyclase?
a2 and B receptors
Except for Phenoxybenzamine (PBZ) and related compounds, all α receptor antagonists are (blank) inhibitors
competitive
where do we find the greatest affect of a-1 blockers?
smooth muscle; while present in CNS the effect is extremely small
a2 receptors (inc/dec) intracellular calcium by decreasing cAMP levels
incerease intracell calcium
a2 receptors (enhance/limit) sympathetic outflow
limit
a2 receptors increase (blank) tone and therefore parasympathetic outflow
vagal tone
what type of receptor increases PLT aggregation in the periphery?
a2
a2 receptors decrease the release of which two neurotransmitters in the periphery?
NE and ACh
What is the effect of a2 stimulation on insulin release and lipolysis?
decreases both
T/F: a2 stimulation decreases lipolysis indirectly
false; directly acts on fat cells
what receptor class increases insulin release?
b
what do we use a1 blockers for?
decrease blood pressure
is the decrease in BP from a1 blockers more noticeable when standing or lying down?
standing
what can exacerbate the lowering of the BP after giving an a1 blocker?
hypovolemia
what mechanism compensates for the lowering in BP from a1 blockers?
baroreflex:
increase HR and CO
If an a1 blocker is mixed with a (blank) blocker, it can exaggerate the baroreflex by leading to the release of NE which activates B1 receptors
a2 receptors on a peripheral nerve ending
a1 blockers will inhibit the effects of (blank) drugs adminstered externally
sympathomimetics; can use to reverse an adverse effect
what is the pure a1 agonist and blocker?
agon: phenylephrine
blocker: prazosin
what is the pure a2 agonist and blocker?
agon: clonidine
blocker: yohimbine
what is the pure b1 agonist and blocker?
agon: dobutamine
blocker: metoprolol
what is the pure b2 agonist and blocker?
agonist: terbutaline
no blocker
t/f: a2 blockers target both the CNS and the periphery
true
what are the effects of a2 blockers on the periphery?
increase release of NE from nerve endings
what is the effect of a2 blockers on the CNS?
increase sympathetic outflow; increase BP
which a1 and 2 blocker binds irreversibly via covalent modification?
PBZ/phenoxybenzamine
what are the effects of phenoxybenzamine in the periphery?
block a receptor in SMC leads to decrease in peripheral resistance
enhanced baroreflex
what are the effects of phenoxybenzamine in the CNS?
increase sympathetic outflow
tachycardia due to a2 block
why would epi produce severe hypotension if given alongside phenoxybenzamine
PBZ blocks epi a action, therefore unapposed b2 action, therefore loooots of SMC relaxation
why do you get hypotension when standing when taking PBZ?
lack of vasomotor reflex from baroreflex
at high doses PBZ irreversibly binds to what three other neurotransmitters?
Serotonin
histamine
ACH
what is the half life of PBZ?
less than 24 hours
what is the use of PBZ?
pheochromocytoma: lots of catecholamines means HTN; PBZ lowers the BP by blocking cat. action
what is the non-serious use for PBZ?
benign prostatic hypertrophy in men
Besides postural hypotension, what are the other side effects of PBZ?
nasal stuffiness; miosis
sexual dysfunction in men
which drug blocks a1 and a2 similarly via reversible competitive inhibition?
phentolamine; PTL
what are the two “classic” a blockers?
phenoxybenzamine and phentolamine
Beside the cardio effects of PTL (which are similar to PBZ), what are the other effects of PTL on other organ systems?
stimulates GI smooth muscle and enhances gastric acid secretion
(phentolamine/phenoxybenzine) can be used to rapidly alleviate a hypertensive episode
phentolamine
what happens when you get extravasation of phenyelephrine?
necrosis
do you use PBZ or PTL for Raynaud’s?
PTL
which a blocker do you give during rapid clonidine withdrawal or tyramine rich foods during MAOI Tx?
phentolamine
what are the cardiac SE of phentolamine?
hypotension reflex tachycardia arrhythmia ischemic events MI
what are the GI SE of phentolamine?
abdominal pain
nauseua
PUD exacerbation
what two conditions contraindicate the use of phentolamine?
PUD and CAD