This site is 100% ad supported. Please add an exception to adblock for this site.

Block 3: vasodilators


undefined, object
copy deck
Name three vasodilators
sodium nitroprusside
name an alpha1 blocker
name two adrenergic inhibitors
name two alpha2 agonists
name a beta-adrenergic antagonist
name two calcium channel blockers
What is the most common form of hypertension
a 5-6 mmHg decrease in diastolic pressure reduces the probability of strokes by...
BP =
CO =
what does hydralazine do

direct relaxation of arterial vascular smooth muscle with little effect on venous and capacitance vessels
what is a serious adverse effect of hydralazine
baroreceptor reflex mediated stimulation of the sympathetic nervous system evoked by the vasodilation and decreased BP -> inc heart rate, contractility, plasma renin and fluid retention
what can the increased contractility and oxygen demand of the heart in response to the baroreceptor reflex of hydralazine cause
cardiac ischemia --> CONTRAINDICATED in patients with CAD and patients over 40
What is given to minimize the adverse effects of hydralazine
sympatholytic agents
when is hydralazine most often used
oral antihypertensive during pregnancy
what does minoxidil do?
nothing, first it has to be metabolized to minoxidil sulfate
what does minoxidil sulfate do
activates the ATP-modulated potassium channel in ARTERIOLE smooth muscle --> hyperpolarization and relaxation with little effect on venous and capacitance vessels
what is an adverse effect of minoxidil
reflex barorecept increase in heart rate, contractility, plasma renin and fluid retention which counteracts the antihypertensive effect of minoxidil
as with hydralazine, what can the increased contractility and oxygen demand in the heart after minoxidil administration lead to
cardiac ischemia --> CONTRAINDICATED in patients with CAD and ventricular hypertrophy
what is coadministered with minoxidil to minimize adverse effects
sympatholytic agents (beta antagonists)
What occurs with topical minoxidil treatment
hair growth --> Rogaine
**can still have measurable cardiovascular effects in some people
what does sodium nitroprusside do?
nothing, it has to be activated to nitric oxide
what does nitric oxide do
activates guanylate cyclase-> cGMP -> activates GMP dependent myosin light chain phosphatase -> dephosphorylates myosin light chain -> decreased contractile state of smooth muscle -> vasodilation in ARTERIOLES and VENULES
why must sodium nitroprusside be given by continuous IV infusion
it is unstable and decomposes when exposed to light
what does prazosin do
alpha blocker - reduces arterial resistance and venous capacitance by inhibiting the vasoconstriction induced by endogenous catecholamines
what is the major adverse effect of alpha blockers like prazosin
first dose phenomenon = orthostatic hypotension in ~50% of patients
- most likely to occur if patients are taking beta antagonists or diuretics
are alpha blockers like prazosin typically effective as a sole treatment for hypertension
no- they typically evoke Na and water retention
what does guanethidine do
inhibits adrenergic function- inhibits PERIPHERAL postganglionic adrenergic neurons -> concentrated within the neurosecretory vesicles where it replaces and depletes the active transmitter norepinephrine
what are the adverse effects of guanethidine due to
sympathetic dysfunction- postural hypotension, sexual dysfunction, diarrhea
what does reserpine do
inhibits adrenergic function- binds to storage vesicles in central and peripheral adrenergic neurons, interferes with a transmitter uptake system and renders vesicles dysfunctional -> nerve endings lose their ability to concentrate and store norepi and dopamine
what are adverse effects of reserpine
sedation, and inability to concentrate and severe depression
what does methyldopa do
central sympatholytic agent (alpha 2 agonist)- acts centrally to reduce sympathetic activity by depleting neuronal stores of norepi
what is the metabolism of methyldopa
converted by adrenergic neurons -> alpha-methyl-dopamine -> alpha-methyl-norepinephrine -> substituted for norepi in secretory vesicle
when is methyldopa often used
as an oral antihypertensive during pregnancy
what does clonidine do
alpha 2 agonist that reduces the activity of neurons in the brainstem responsible for generating and maintaining sympathetic activity
what happens in clonidine overdose
can activate alpha 2 receptors on vascular smooth muscle cells causing vasoconstriction
name some adverse effects of methyldopa and clonidine
dizziness, reduced libido, sedation and depression
what can sudden withdrawal of alpha 2 agonists cause
withdrawal syndrome with blood pressure rising to levels above those that were present prior to treatment
how do calcium channel blockers work
block Ca influx through voltage gated calcium channels in arterial smooth muscle -> prevents Ca from binding calmodulin ->prevents myosin light chain kinase from phosphorylating myosin light chain -> prevents interactions between myosin and actin -> DECREASING vascular resistance and BP
do calcium channel blockers work on venous smooth muscle
no, only arterioles
name two dihydropyridine calcium channel blockers
name a non-dihydropyridine calcium channel blocker
how do dihydropyridine calcium channel blockers differ from non-dihydropyridine calcium channel blockers
nifedipine and amlodipine cause baroreceptor reflex increase in sympathetic activity and tachycardia; verapamil reduces BP without evoking tachycardia due to an additional direct negative chronotropic effect
What is a consequence of the direct arteriole vasodilation of calcium channel blockers
they may increase venous return -> CONTRAINDICATED in patients with impaired cardiac function such as ventricular hypertrophy, ischemic heart disease, or CAD
What has nifedipine actually been shown to do
increase the risk of ischemic heart disease
in what patient population can long acting calcium channel blockers be well tolerated
patients with angina and arrhythmia; can be effective monotherapy in low-renin populations (elderly and African-American populations)
name adverse effects of calcium channel blockers
cardiac depression
cardiac arrest
AV block
congestive heart failure
Coronary vasodilation...
peripheral vasodilation...
Rate of recovery of Ca channels...
AV conduction...
Coronary vasodilation...++++
peripheral vasodilation...++++
Contractility...REFLEX INC
Rate of recovery of Ca channels...NO CHANGE
AV conduction...NO CHANGE
Coronary vasodilation...
peripheral vasodilation...
Rate of recovery of Ca channels...
AV conduction...
Coronary vasodilation...++
peripheral vasodilation...++
Rate of recovery of Ca channels...DECREASE
AV conduction...SLOWS
what does propranolol do
a beta adrenergic antagonist- reduces myocardial contractility and cardiac output by blocking any endogenous sympathetic beta1 stimulation of the cardiac SA node and ventricular muscle
what do beta antagonists like propranolol do to renin and angiotensin II
reduce renin and decrease angiotensin II
what is propranolol useful for
treatment of angina and arrhythmias; may decrease mortality after acute myocardial infarction by about 10%
what population may have a lesser antihypertensive response to beta andrenergic antagonists like propranolol
elderly and African Americans
name adverse effects of propranolol
erectile dysfunction
in what population is propranolol contraindicated in
patients with asthma since blocking beta2 receptors can lead to bronchoconstriction

Deck Info