Test 3: 33 cardio drugs Flashcards
how do vasodilators effect arterial blood pressure
decreases total peripheral resistance (arterial vascular smooth muscle tone →vasodilation = ↓afterload)
↓ venous return to the heart = ↓preload
how do positive inotropic drugs effect arterial blood pressure
change myocardial contraction which changes stroke volume → changes cardiac output
— are some common ace inhibitors
benazepril
enalapril
type of vasodilator
— is a type of ARB
telmisartan
— are two inotropes used in vet med
digoxin and pimobendan
arteriodilators can decrease mitral regurgitation in dogs with DCM by
increasing the size of the aorta= decrease afterload
will cause more blood out through the aorta and less going backwards into the atrium
— is a venous dilator medication
nitroglycerin
— are balanaced vasodilators
ACE inhibitors (enalapril)
Nitrates (nitroprusside)
— are arteriodilators
hydralazine
amlodipine
goal of ACE inhibition
stop angiotensin II which causes
fluid and Na retention
vasoconstriction
increased thirst
vascular and myocardial fibrosis and pathologic tissue remodeling
increases aldosterone
which ACE inhibitor is less toxic in patients with exisiting renal disease
Benazepril
what is an ARB
angiotensin II receptor blocker
telmisartan
bind to AT1 receptors which cause hypertension and vasocontriction
does not bind to AT2 receptors which cause good things: vasodilation and Natriuretic
side effects of ACE inhibitors
hypotension
renal impairment (need to check renal function after starting meds)
↑ potassium
anorexia, diarrhea, vomiting
cough?
enalapril
if patient gets cough on ACE inhibitor then can start —
ARB (telmisartan)
what are the three main nitrates used
nitroglycerin
isosorbide (mono-, di-) nitrate
nitroprusside
how do nitrates work
exact mechanism not known but nitrates cause the release of NO which will cause vasodilation by the formation of cGMP
why do paitents become tolerant to nitrates
↓ sulfhydryl(SH) groups
can prevent tolerance by staggered therapy- give for 5 days, give weekend off
Isosorbide mononitrate is metabolized where
not the liver
how do arteriodilators reduce myocardial workload
- reduce systemic BP
- reduce afterload and myocardial wall stress
- unloads the failing heart
what happens with high dose IV nitroprusside
toxic
coverts to methemoglobin which pushed curve to the left: RBC won’t let go of O2
nitroprusside: balanced vasodilator: both arteriodilator and venodilator
when to use nitroprusside
bad cases of CHF that are not responding to normal therapy
HTN crisis
does not need SH to release NO → vasodilation
balanced vasodilation: both arterio and venodilator
adverse effects of nitroprusside
hypotension
reflex tachycardia
does not need SH to release NO → vasodilation
balanced vasodilation: both arterio and venodilator
how does hydralazine work?
unknown
increases cGMP → vasodilation= ↓afterload
adverse effects of hydralazine
hypotension
reflex tachycardia
GI: vomiting and anorexia
— is a dihdropyridine calcium channel blockers
amlodipine
treat ↑BP with no effect on heart rate or inotropic state
— are non-dihydropyridine calcium channel blockers
verapamil
diltiazem
will ↓BP and control HR (antiarrhthymic)
side effect of amlodipine in dogs
gingival hyperplasia
amlodipine: dihdropyridine calcium channel blocker that ↓ BP without effecting HR
— are naturally occurring catecholamines
sympathomimetics
epinephrine
norepinephrine
dopamine
what 4 receptors are effected by beta agonist in the heart
L type Ca channel
phospholamban
Troponin I
RYR2
— drugs work on the beta adrenergic receptor in the heart
dopamine
dobutamine
— is a phosphodiesterase inhibitor
pimobendan (balanced vasodilator)
— drugs works on the Na/K ATP pump in the heart
digoxin
compare effect of dopamine nad dobutamine on systemic vascular resistance and cardiac output
how does pimobendan work
increases binding of Ca to troponin in the cardiac cell = ↑ myocardial contractility
does not increase the amount of Ca in a cell and does not increase energy demand of the cell
inhibits phosphodiesterase
will also cause arterio and venodilation
compare pimobendan and digoxin
primobendan increases contractility of heart by increasing troponins sensitivity to Ca that is already there= no increase in Ca into the cell and no increase in energy demand of the cell
digoxin will inrease the amount of Ca into a cell to cause increased contraction
if you give pimodendan to dog with asymptomatic heart disease what will happen
reduces onset of CHF for average of 15 months
how does digoxin effect HR
slows conduction by SA node
slows conduction through AV node
increases refractory period in the AV node
used to treat Afib
what happens with digoxin toxicity
narrow therapeutic window
cause cardiac arrhythmias (AV block, ventricular bigeminy)
Vomiting, diarrhea, anorexia and weight loss
depression
how to prevent digoxin toxicity
start at low dose
dose on body surface area
check a serum level after 5-7 days
how to treat digoxin toxicity
stop drug
treat symptoms
can give antibody Digibind
if symptoms resolve can restart at lower dose
dopamine at low dose
B receptor: increases HR and contactility, cause vasodilation
at high dose: binds to alpha adrenergic receptors and causes vasoconstrictiona and ↑HR
dopamine at high dose
act on Alpha 1 receptors
cause vasoconstriction and ↑HR
at low dose: B receptors: ↑HR and contractility
sopaminergic receptors cause vasodilation
— is primary ⍺1 agonist vs — is primary β1 agonist
dopamine (cause vasoconstriction and ↑HR)
dobutamine ( inotropic agent= increases intracellular Ca= increase contraction with minimal effect on heart rate)
what does a B1 adrenergic agonist do
dobutamine
increases contraction of the heart without effecting HR
does not increase O2 demand of the heart
dopamine or dobutamine should be given to treat CHF
dobutamine: B1 receptor= + inotropic drug= increases contraction of the heart
dopamine is a vasopressor= alpha 1 receptor= cause vasocontraction and increases systemic vascular resistance = used to treat sepsis
— increase myocardial contractility and are used in the setting of heart failure.
Positive inotropic agents
(catecholamines/dobutamine, digoxin→increase Ca into a cell)
(pimobendan →increase binding of Ca to myosin)
