ANS Pharm: Adrenergic Antagonists Flashcards
Common side effect of prazosin
ortho hypoTN
Why shouldn’t hypovolemic patients get A1 antagonists?
reduction in arterial BP
&
reflex tachycardia
Drugs that affect the ANS may mimic or block these 2 NTs
ACh & NE
propranolol
(nonselective, so less popular now)
Why is labetalol special in its action?
has both selective A1 antag + B1 & B2 antag
vasodilates without reflex tachycardia
alpha : beta blockade is 1:7.
Alpha antagonits are good for HTN, __, ___, & ___
heart failure
BPH
pheochromocytoma
Why do we need to carefully titrate alpha & beta antagonists?
susceptible to variable response based on receptor up/down regulation (both), receptor densities in diff tissues (alpha), & genetics (beta)
the nonselective & selective Alpha antag.
Which is competitive? non-competitive?
phentolamine = competitive
phenoxybenzamine = non-competitive (IRREVERSIBLE)
phenoxybenzamine = prototype nonselective
The only way to stop phenoxybenzamine’s effects
non-competitive (IRREVERSIBLE) non-selective apha antagonist
synthesize new receptors
you gave phenoxybenzamine but now have hypoTN. Which pressors will NOT work?
- norepi & neo d/t the irreversible block
- epi may worsen HypoTN d/t unopposed B2 stimulation (“epi-reversal”)
“epi-reversal”: epi’s A-mediated pressor turns into B-mediated depressor
Expected effects from phenoxybenzamine
use low dose initiation
- blocks A-activity of epi & NE (↓SVR)
- reflex tachycardia (baroreceptors & increased free NE)
- ortho hypoTN; fall risk
best treatment for phenoxybenzamine hypoTN
vaspressin and fluids
NO!: epi, norepi, neo
how to reverse phentolamine
A-agonist
(neo, NE)
phenoxybenzamine cannot be reversed; only by making new receptors
phentolamine has an affinity for ___ receptors, which….
5HT
- stomach acid secretion
- mast cell degranulation
Mast cell degranulation: release inflammatory substances (histamine, TNF-α, tryptase)
Prazosin selectivity
A1:A2
1000:1
Prazosin
expected effects
↓PVR in arterioles and veins
↑venous capacitance, ↓preload
little change in HR
ortho hypoTN
prazosin
which selective A-antagonist is mainly used for BPH?
terazosin
less potent, longer doA
Why do we care if a patient is on a -“zosin”?
selective A-antag
may worsen ANE induced hypoTN
Yohimbe effects
not used as HTN Rx anymore, but still present illegally in supplements
selective A2 antag
- ↑PNS/cholinergic activity
- ↓SNS/adrenergic activity
- may lessen effects of anti-HTN drugs
What happens if you sudddently stop taking your Beta blocker?
risk rebound HTN and tachycardia
bradyarrhythmias from beta blockers may impair the response to…
- hypovolemia
- progressive heart block
- heart failure
- bronchoconstriction
propranolol & acebutalol
Beta blockers
intrinsic sympathomimetic activity (ISA)
partial beta stimulation (agonist)
+
blocking endog. catechols. from binding to Beta receptors
(less potency than catecholamine & other BBs)
labetalol!!
- bronchconstriction
- hypoglycemia
- periph. vasoconstriction
Dont give this BB to Raynaud’s & periph. vascular Dz
propranolol
blocks B2 = periph. vasoconstriction
Propranolol
moA
the prototype nonselective BB
- competitive
- B1 & B2 antag.
- blocks epi, NE,DA, dobutmaine, isoproterenol
The nonselective BBs
- Propranolol
- Nadolol
- Pindolol
- Labetalol
- Sotalol
- Carvedilol
- Timolol
BB w/ very long HL
Nadolol
Blocking Beta receptors will decrease conduction through the ___ node
AV
- metoprolol
- acebutalol
- esmolol
- bisprolol
which selective BB has weak B agonist effects (ISA)?
acebutalol
less bradycardia and BP effects
T/F:
Giving higher doses of selective BB’s will decrease the selective action.
True!
higher dose = less selectivity
metoprolol
metoprolol
moA
- competitive cardioselective (B1)
- blocks epi and NE
- can be used in HR
metoprolol
max dose
15 mg
give as 2.5 -5 mg
these two selective BBs block epi and NE
metoprolol & esmolol
Why is esmolol first line for rapid periop control for HR & BP
- fast onset
- brief doA (<15 mins)
- can titrate as it causes DD ↓HR
esmolol
esmolol dose
- 10-80 mg bolus
- 50-300 mcg/kg/min drip
Does esmolol have ISA or MSA?
not at clinical doses
esmolol metab
nonspecific esterases from RBCs
atenolol
which BB decreases conductivity & intotropy from NE release?
atenolol
Labetalol
receptor activity
unique! (ISA)
A1 & Beta antag.
B : A block
7 : 1
Labetalol
primary indication
acute HTN
Labetalol’s mixed activity (A1 & Beta antag) produces ____ without ….
vasodilation
baroreceptor HR increase
Labetalol HL
6H
Labetalol dose
2.5 mg increments
highly variable responses!
may acutely exaggerate existing bradycardia
Labetalol & Carvedilol
Both are nonselective BB’s, how does their action compare?
both A1, B1, B2 antagonism
carvedilol has more modest HR reduction; caution w/ labetalol
this BB has antioxidant & anti-inflammatory properties
carvedilol
atenolol
