ANS pharmacology & pathophysiology 3 Flashcards
A common side effect of prazosin is:
a. diuresis
b. severe bradycardia
c. orthostatic hypotension
d. excessive energy
c. orthostatic hypotension
Alpha 1 adrenoreceptor antagonists
reduce arterial BP but can also trigger reflex tachycardia and orthostatic hypotension
Examples of nonselective alpha antagonists are
phenoxybenzamine and phentolamine
Examples of selective alpha antagonists are
prazosin
tamsulosin
yohimbine
Beta-blockers are used to manage
hypertension
CAD
MI
heart failure
The prototypical B-adrenoreceptor antagonist nonselective is
propranolol
The alpha receptor antagonist are used to treat
HTN
HF
BPH
pheochromocytoma
Phenoxybenzamine is a (moa
noncompetitive a antagonist
blocks the alpha mediated activity of NE and EPI resulting lower peripheral vascular resistance and BP
What is used exclusively in the preoperative management of pheochromocytoma to normalize BP and prevent episodic hypertension?
phenoxybenzamine
Phenoxybenzamine produces an irreversible block rendering ______________ ineffective in treating phenoxybenzamine-induced severe hypotension
norepinephrine and phenylephrine
The best treatment for phenoxybenzamine-induced severe hypotension is
vasopressin and fluids
What is the MOA of phentolamine?
competitive nonselective alpha receptor antagonist
Unlike phenoxybenzamine, the receptor interaction with phentolamine can be overcome by
using an alpha receptor agonist such as phenylephrine or norepinephrine
Phentolamine should be used with extreme caution in patients with
flow-limited coronary artery disease b/c it causes baroreceptor mediated reflex tachycardia
What is the half-life of phentolamine?
<10 minutes
Phentolamine may have a benefit in treating otherwise
refractory HTN that may be seen with abrupt clonidine discontinuation
_________ can be used as a local infiltration injection after IV extravasation of a vasoconstrictor to prevent tissue necrosis.
Phentolamine
What is the MOA of prazosin?
highly selective alpha 1 receptor antagonist
Is there a change in HR with prazosin?
No
Side effects of prazosin include
postural/orthostatic hypotension
The following three drugs are analogs of prazosin:
terazosin
doxazosin
tamsulosin
The main uses of terazosin, doxazosin, and tamsulosin are to treat
BPH
Terazosin, doxazosin, and tamsulosin anesthetic complications:
these drugs can exacerbate anesthetic-induced hypotension
Yohimbe (MOA)
selective alpha 2 adrenergic antagonist
What is yohimbe used for?
erectile dysfunction
athletic performance
weight loss
hypertension
diabetic neuropathy
Yohimbe can diminish the
antihypertensive effect of other antihypertensive medications
Indications for a beta-blocker include
hypertension
supraventricular tachycardia
afib
blunting an acute hemodynamic response, CHF, and conditions of ischemic heart disease
reducing myocardial O2 consumption and improving perfusion
Concerns with beta blockers include
bradyarrhythmias
obtunding the CV response to hypovolemia
progressive heart block
heart failure
bronchoconstriction
Abrupt discontinuation of long-term use of beta blockers can result in
rebound tachycardia and hypertension
Some beta blockers (propranolol and acebutolol) have
membrane stabilizing activity–> act as antiarrhythmics
Some beta blockers (pindolol, labetalol, & acebutolol) possess _________
intrinsic sympathomimetic activity (has a partial stimulating action while also blocking endogenous catecholamines)
Antagonism of B2 receptors can produce
bronchoconstriction
hypoglycemia
peripheral vascular constriction (can aggravate Raynauds or PVD)
_________ has a very long half-life
Nadolol
___________ has some weak beta agonist effects and is associated with less slowing of HR and less of an impact on BP
Pindolol
Examples of nonselective B-adrenergic antagonists include
carvedilol
nadolol
pindolol
sotalol
timolol
propranolol
Beta 1 blockers include
metoprolol
atenolol
esmolol
bisoprolol
acebutolol
_________has some weak beta agonist effects and is associated with less slowing of HR and less of an impact on BP
acebutolol
What is the MOA of metoprolol?
competitive, cardioselective B1 receptor antagonist
What is the dose of metoprolol?
administered IV 2.5-5 mg increments to a max dose of 15 mg
What is the first-line drug for rapid perioperative control of HR & BP?
esmolol
swift onset & brief duration of action (<15 minutes)
Esmolol is metabolized by
nonspecific esterases found in the RBC
What is the dose of esmolol?
bolus: 10-80 mg or an infusion (50-300 mcg/kg/min.)
What is the MOA of labetalol?
adrenergic antagonist with alpha 1 and nonselective beta adrenergic antagonist effects
The primary indication of labetalol is
acute hypertension
The B2 antagonism of labetalol can produce
bronchospasm in patients with asthma or COPD
Carvedilol MOA:
antagonist at alpha 1 and B1 & B2 adrenergic receptors
Which beta-blocker has intrinsic sympathetic activity (ISA)?
labetalol
Which beta receptor antagonist undergoes renal metabolism?
atenolol
