Pharm Quiz 3 - Cardio Drugs Flashcards
What is the main effect of inotropic drugs?
increase contractile force, used for CHF
Where does fluid accumulate in left sided heart failure?
lungs - pulmonary edema
What are the 3 cardiac glycosides?
digoxin, ditioxin, ouabain
What is the MOA for cardiac glycosides?
positive inotropic by inhibition of Na/K -ATPase enzyme in sarcolemmal membrane of cardiac muscle –>increases calcium availability
What does the Na/K ATPase enzyme have to do with calcium availability in the heart?
Na accumulates, uses calcium exchanging mechanism instead
What effects does digitalis have on the cardiac rate and rhythm?
decreased HR by slowing discharge rate of SA node and AV conduction, prolongs refractory period for AV conduction
How does digitalis enhance cardiac excitability?
partially depolarizes cell –>reduces disatolic potential to threshold level
How does digitalis cause diuresis?
effect of digitalis increasing blood flow (not a direct effect)
Why does IV digitalis induce vomiting in dogs?
stimulation of CTZ (chemoreceptor trigger zone), not protected by BBB
What are the side effects of dogs taking digitalis orally?
vomiting, protracted diarrhea –> toxicity
What should be considered for the dosage for digitalis?
dose by lean body weight to avoid overdose in obese animals. weight of fluid from edema should be deducted in estimate. dose reduced in animals with kidney and liver dz
What are the 2 clinical indications for digitalis?
CHF - left and right
Atrial arrhythmias - esp. atrial fibrillation and flutter
What are the 3 different dosing methods used for digitalis?
Slow method - cardiac failure, 5 equal parts over 48 hrs
Rapid - 3 equal parts every 6 hours over 24hrs
Intensive - emergency, one half loading dose given initially, one fourth at 6 hrs, one eight, at 4-6 hr intervals
When will steady state concentration be attained in digitalis therapy?
6th-8th day of maintenence therapy
What are the differences in dosing digitalis for cats?
no loading dose, more sensitive
When should IV digitalis be given to an animal?
doesn’t retain oral meds
acute cardiac decompensation
respiratory distress
When should IM digitalis be given?
Not preferred, causes pain and swelling
What is useful in determining if an animal has a digitalis toxicity?
ECG
plasma/serum digoxin conc
serum K+ concentration
What are the effects of digitalis toxicity on the heart?
reduced sinus rate and slowed AV conduction –> heart block
ventricular bigeminal rhythm (extra QRS after reg. systole)
What electrolyte imbalance potentiates digitalis arrhymogenecitiy?
hypokalemia (and hypercalcemia)
What electrolyte imbalance antagonizes digitals arrhyogenecity?
hyperkalemia
Why does potassium have antiarrhythmic activity?
inhibition of cardiac glycoside binding to Na-K-ATPase enzyme
What should be done to treat mild digitalis toxicity?
oral potassim
What should be done to treat severe digitalis toxicity?
cholestyramine resin –> increases glycoside secretion
anti arrythmia drugs
atropine - for sinus bradycardia
What can be administered with digitoxin to abolish atrial dysarrhythmias?
quinidine
Which species does quinidine increase the steady state plasma of digoxin two-fold? What is the MOA?
horses and dogs
quinidine blocks tissue binding sites and P-glycoprotein
What is the preferred loop acting diuretic for CHF? What is it’s MOA?
furosemide
inhibits Na+/K+/2Cl- co transport
Where do thiazide diuretics act in the kidney? What effect does it have on digitoxin?
Na+/Cl- exchange in DCT
increases Ca+ reabsorption
increases toxic potential of digitoxin
What is the MOA for potassium sparing diuretics?
antagonizes aldosterone, inhibits reabsorption of sodium
What is the limitation of potassium sparing diuretic?
slow onset of action
What combination of diuretics would produce diuresis without delayed onset or excess potassium excretion?
hydroflumethiazide and spironolactone
What is the MOA of phosphodiesterase inhibitors?
inhibit phospho –>increases concentration of cAMP –>increased cardiac contractility and vasodilation
What is the clinical use of inamrinone and how is it given?
acute myocardial failure , IV
What side effects do phosphodiesterase inhibitors have in humans and may be in dogs?
tachyarryhtmias
What is the phosphodiesterase inhibitor drug that increases the binding efficiency of cardiac myofibril to calcium ions?
pimobendan
What receptor does dobutamine act on?
B1 agonist (B-adrenergic agonist)
What are the two drawbacks of dobutamine?
arrhythmias
tachyphylaxis - tolerance
What are the uses of dobutamine?
dilated cardiomyopathy (CHF)
shock
hypotension during anesthesia in horses
What are the effects of aminophylline on the heart?
chronotropic and weak inotropic –> inhibition of phosphodiesterase
also bronchodilation
What are the uses of aminophylline?
acute pulmonary edema
What are the 3 phosphodiesterase inhibitors?
inamrinone
milrinone
pimobendan
What is the main drawback of vasodilators?
reflex tachycardia increases heart oxygen demand
What drug can compensate the marked hypotension produced by sodium nitroprusside?
dobutamine
What is the use of sodium nitroprusside?
vasodilator in both arteries and veins in hypertensive emergencies
What are the two arteriolar vasodilators?
Hydralazine
minoxidil
What is the MOA of hydralazine and minoxidil?
opening of potassium channels in arteriolar smooth muscle
What are the side effects of hydralazine and minoxidil?
tachycardia
What vasodilator drug is a alpha 1 adrenergic antagonist?
prazosin
minimal reflex tachycardia
What does nitroglycerin do? How is it administered?
relaxation of large veins (and arteries), topical for dogs and horses, angina in humans
Which vasodilator is a B-2 adrenoreceptor agonist? Where does it act on?
isoxsuprine - skeletal muscle vasculature
What is isoxsuprine used for?
navicular dz and laminitis in horses
Which calcium channel blocker is used for hypertension in cats?
amlodipine
What drug is a phosphodiesterase V inhibitor and used for canine pulmonary hypertension?
sildenafil
What ace inhibitor is from pit viper venom?
captopril
What are the two ace inhibitor pro-drugs?
enalapril maleate and benazepril hydrochloride
What are the 2 ways ace inhibitors act?
inhibits peptidyl dipeptidase which hydrolyses angiotensin 1 to 2
inhibition of bradykinin degradation
What are the 3 goals of treatment of acute left ventricular failure?
- improve gas exchange
- enhance myocardial contractility
- reduce workload of the left ventricle
What drug is contraindicated in acute left ventricular failure?
epinphrine –> vasoconstriction, arrythmogenecity
What are the 3 drugs used to treat acute left ventricular failure?
furosemide
morphine sulfate
digoxin
What are the 4 classes of antiarrythmic drugs and what is their MOA?
1-membrane stabilizer/local anesthetic
2- B-adrenergic antagonist
3-prolong refractory period
4-calcium channel blockers
What are the 3 subclasses of class 1 antiarrythmic drugs and their action?
A-prolong cardiac action potential and refractory period
B-reduction in phase 0 depolarization and conduction velocity in injured tissue
C- ?
What antiarrythmic drugs produce “pure” prolongation of action potential?
class III
What is the prodrug of class IV antiarrhythmic drugs?
verapamil
What is the use of Class IV antiarrythmic drugs?
supraventricular tachyarrhythmias and ventricular hypertrophy in dogs and cats
What arrythmia are digitalis glycosides good at treating?
atrial tachyarrythmias
What is the example of pharmacodynamic interatction of antiarrythmic drugs?
quinidine inhibits oxidative metabolism of beta blocker
What are the 2 examples of pharmacokinetic interactions of antiarrythmic drugs?
quinidine displaces digoxin from tissue binding sites
diltiazem competitively inhibits renal tubular secretion of digoxin
What is quinidine always preceded by?
treatment with digitalis digoxin
What are the 2 ways quinidine controls atrial tachyarrythmias?
directly prolongs refractory period
indirectly lengthens refractory period (anticholinergic)
What are the clinical uses of quinidine and what animals are an exception to the treatment?
ventricular premature complexes
atrial fibrillation - not in small breed dogs
What is the contraindication for quinidine?
not recommended in AV blck or interventricular block
How is quinidine adminestered to horses for atrial fibrillation?
nasogastric tube
What are the adverse effects of quinidine in horses?
urticaria, GI, inflammation of nasal mucosa, laminitis
Which other Class IA drug is similar to quinidine?
procainamide hydrochloride
What is procainamide better at treating than quinidine?
ventricular arrythmias (because of antimuscarinic effect)
What are the signs of procainamide toxicity?
widening of the QRS complex of the ECG, additional arrythmias or hypotension
What side effects of disopyramide limit it’s use in vet med?
rapid metabolism
short half life
atropine like side effects
negative inotropic effects
What is phenytoin sodium used for?
digitalis-induced arrythmias and ventricular arrythmias
What is the MOA of phenytoin sodium?
improves impulse conduction through damaged cardiac tissue
What drug increases the risk of phenytoin toxicity?
chloramphenicol - inhibits metabolism of phenytoin in liver
What are the signs of phenytoin toxicity?
postural ataia and hypermetric gait
What is lidocaine used to treat arrythmia wise?
ventricular dysrhythmias during GA
cardiac emergenices to antagonize epinephrine
What antiarrythmia drug is a structural congener to lidocaine?
tocainide
What are the advantages of using tocainide?
effective after oral admin
long duration of action
What is the use of mexiletine?
ventricular arrythmias that are lidocaine sensitive
What class IB agent has a broader spectrum of antiarrythmic activity?
aprindine
What are the SE of aprindine?
leukopenia, agranulocytosis
hepatoxicosis, hypotension, contractile response
What drug should be used as an alternative strategy for controlling ventricular arrythmias in dogs?
aprindine
What is the new aprindine congener that is 6x more potent?
indecainide
What drugs are effective in controlling the cardiac arrythmias due to sympathetic overactivity?
propanolol hydrochloride (oxprenolol, metoprolol, timolol, aprenolol, pindolol, practolol)
What effects does propranolol have on the heart?
slows spontaneous discharge of SA and ectopic pacemakers
slows antegrade and retrograde conduction
increases refractory period
What are the conditions which propranolol can treat?
supraventricular tachycardia
tachyarrythmias associated with digitialis and physical exertion
arrythmias by inhalents
What is the SE of propranolol?
non selective B blocker –> not recommended for COPD
What is the drug that can be used for COPD patients?
metoprolol tartrate - B1 blocker
What are the precautions when using beta blockers?
when used in patients with reduced cardiac reserve (CHF)
What are the 2 class III antiarrythmic drugs?
bretylium
amiodarone
What arrythmias can bretylium is contraindicated?
animals anesthesized with halogenated anesthetics (sensitizes myocardium to catecholamines)
What are the effects of amiodorone?
prolongs action potential and refractory period
also has long half life
What class IV drug is a systemic and coronary vasodilator?
verapamil
What is the unique MOA of verapamil?
selectively inhibiiting transmembrane influx of Ca++ in cardiac
What arrythmias can verapamil control>
impulse formation (automaticity) or impulse conduction (re-entry)
What are the adverse effects of calcium channel blockers?
decreased contractile response, reduced CO –> reduced cardiac decompensation in heart failure patients and induces pulmonary edema and dyspnea
What are the clinical indications of epinephrine? (3)
anaphylaxis
cardiac arrest
prolong duration of lidocaine
What are the contraindications of epinephrine?
acute left ventricular failure
cardiac emergenccies during anesthesia
What happens when an animal with blocked alpha 1 receptors is given epinephrine?
depressor effect rather than pressor response (epinephrine reversal)
What are the 2 clinical indications of isoproterenol?
short term emergency of heart block
cardiac arrest
What receptors are effected by isoproterenol?
B1 - increases CO
B2 - dilation of sk. muscle and relax bronchial sm muscle
Where does dopamine cause vasodilation the most?
renal and splanchnic arterial beds
What effects does dopamine have on the heart?
positive inotropic action
What are the uses for dopamine?
oliguric renal failure - increased renal blood flow increases efficiency of furosemide
