vasodilators Flashcards
what things relax vascular smooth muscle
- increasing cGMP, NO, nitrates, PDE5 inhibitors
- decreasing intracellular Ca
- Ca channel blockers (CCBs)
- increasing cAMP in vascular cells (cAMP increases inactivation of myosin light chain kinase)
what is the purpose of vasodilators
- improve CO
- reduce edema and effusions
vasodilators can affect arterioles and ?
venous capacitance vessels
what drugs are vasodilators
- ACEI
- Nitrites
- Hydralazine
- CCBs
- alpha blockers
what drug that acts through NO is most effective in CHF secondary to mitral valve insufficiency
Hydralazine
Hydralazine dilates ____ but not _____
arterioles
not veins
symptoms of Hyrdalazine toxicity
- V+, anorexia, tachycardia, sweating, hypotension (Cats)
- ischemic arrythmias, decompensation
what happens to nitrate compounds
they get converted into NO
Nitrates preferentially dilate ?
veins but they also dilate arteries
effect of nitrates (NO) on myosin light chains
decreases phosphorylation
these drugs have limited use in VetMed and have questionable efficacy in dogs & cats; all uses are extra label
Nitrates
what are the uses for Nitroglycerin
- pulmoney edema associated w/ HF
What nitrate dugs have potential for tolerance
- Nitroglycerin
- Isosorbide dinitrate
avoid intermittent use
of the 3 nitrate drugs (nitroglycerin, isosorbide dinitrate, sodium nitroprussidae) which one is a potent vasodilator and also doesn’t cause tolerance
Sodium nitroprusside
how is Sodium nitroprusside administered
CRI, constant infusion
what vasodilator is used in patients with pulmonary edema associated w/ HF and hypertensive crisis
Sodium nitroprusside
what vasodilator is used to treat pulmonary edema associated with HF
Nitroglycerin
what are the two important functions of intracellular calcium
- triggers muscular contraction in myocardium + vascular sm
- needed for the pacemaker activity of the SA node and for conduction through the AV node
what opens the heart & vascular smooth muscle Ca channels? what closes them?
- opened by beta adrenergic stimulation to enhance calcium entry
- closd by CCBs to inhibit calcium entry
orally active drugs that bind L-type channels in the myocardium and vascular smooth muscles
CCBs
CCBs will relax all smooth muscles that depend on _____ for normal resting tone & contraction
calcium
what are the major cardiac effects of CCBs (3)
- negative inotropic effects (decreased contractility)
- reduced impulse generation in SA node
- slowed AV node conduction
long acting dihydropyridine Ca channel blocker that causes vasodilation w/out significant cardiac effects
Amlodipine besylate
vasodilator DOG in hypertensive cats , all uses are extra label
Amlodipine besylate
what kind of metabolism does Amlodipine besylate undergo
hepatic
what does Dilitazem do
depresses SA and AV node, causes cardiac contractile depression
what condition is treated using Dilitazem in cats and in dogs (different)
cats - hypertrophic cardiomyopathy
dogs - supraventricular tachycardia
what drug needs to be careful when used in nursing mothers and why
Diltiazem b/c it is excreted in milk
what is the main difference between the effects of Amlodipine and Dilltiazem
- Amlodipine causes more significant vasodilation and reflex tachycardia
- Diltiazem causes depression of SA and AV node and negative inotropic
how do phosophodiesterase 5 inhibitors (PDE5) cause vasodilation
inhibition of cGMP, less cGMP = vasodilation
what condition is Sildenafil useful in treating
pulmonary hypertension in dogs
how do alpha 1 adrenergic antagonists work to decrease blood pressure
- blocking alpha one reduces vasoconstriction in arteries and veins caused by NE
- blood pressure falls due to a decrease in peripheral resistance
what is the primary use of Prazosin
treatment of functional urethral obstruction in dogs
how does prazosin elicit less of a tachycardic reflex
prazosin only targets alpha one receptors, not alpha 2
what are the adverse effects of prazosin
- hypotension
- sodium and water retention (increased renin)
what is the BA of Diltiazem in dogs vs cats
25% in dogs, 50-80% in cats (PO)
of all the vasodilators, which drug has the greatest binding to plasma proteins
Diltiazem, 70-75% bound to plasma proteins
where is Diltiazem metabolized
liver
this drug decreases the membrane Ca current, causes long-lasting relaxation of vascular smooth muscles and decreases cardiac contractility, automaticity and conduction
Amlodipine besylate (CCBs)
