Drugs used in the treatment of CHF

Question 1

Positive inotropic drugs

Answer 1

Digitalis Glycosides

Beta-1 agonists

Question 2

Types of Digitalis Glycosides

Answer 2

Digitoxin
Ouabain
Digoxin

Question 3

MOA of Digoxin

Answer 3

Inhibition of Na+-K+ ATPase in the myocardial cell membrane increases Na+ available for exchange with Ca2+
The result is increase inintracellular Ca2+ which results in a positive inotropic effect

Question 4

Cardiovascular effects of Digoxin

Answer 4

Positive inotrope
Reduction in sinus rate and slowing AV conduction
Prolonged PR intervals in ECG
Increased mechanical efficiency of the failing heart
Normalization of BP and peripheral resistance

Question 5

Digoxin kidney and GI effects

Answer 5

Kidney = Diuretic effect mainly secondary to increased cardiac output
GI = GI irritation, vomiting

Question 6

Digoxin Pharmacokinetics

Answer 6

Administered orally and can be given by slow IV in an emergency
Oral bioavailability is more for the elixir than for the tablet
Half life depends on the species
Small amount metabolized by the liver
Undergoes hepatic recycling
Excretion is mainly renal in dogs and horses, and renal and hepatic in cats

Question 7

Therapeutic uses of Digoxin

Answer 7

CHF

Atrial arrhythmias in dogs

Question 8

Adverse effects of Digitalis Glycosides

Answer 8

Digitalis has a narrow safety margin
Cats are more sensitive than dogs
Tachyarrhythmias
Bradyarrhythmias
GI

Question 9

Adverse effect of Digitalis Glycosides

-Tachyarrhythmias

Answer 9

Predisposing Factors - hypokalemia, hypomagnesemia, hypercalcemia, hypernatrmia, hypothyroidism, hypoxemia
Treatment - drug withdrawal, K+ IV, antiarrhythmic drugs, cholestgramine, Digoxine immuen Fab

Question 10

Adverse effect of Digitalis Glycosides

-Bradyarrhythmias

Answer 10

Treatment - drug withdrawal, Atropine (drug of choice)

Question 11

Adverse effect of Digitalis Glycosides

-GI

Answer 11

Clinical signs - anorexia, vomiting, diarrhea

Treatment - drug withdrawal, fluid therapy

Question 12

Beta-1 agonist drugs and uses

Answer 12

Positive Inotropes
Only used in emergencies
Dopamine
Dobutamine

Question 13

Inodilator drugs

Answer 13

Inamrinone
Milrinone
Pimobendan

Question 14

MOA of Inodilators

Answer 14

In the failing heart, Pinobendanacts by sensitization of the cardiac contractile apparatus to Ca2+ by enhancing the interaction between Ca2+ and troponin C complex
Inhibits phosphodiesterase III and IV = potential to increase intracellular Ca2+ and increased myocardial O2 consumption; minimal effect at therapeutic doses in dogs with CHF
Inhibition of phosphodiesterase III and IV results in vasodilation in arteries and veins = reduction in both cardiac preload and afterload

Question 15

Uses of Inodilators

Answer 15

Approved to treat CHF in dogs
Adjunctive therapy in improving the quality and length of life in dogs with heart failure due to both dilated cardiomyopathy and chronic degenerative valvular disease
Used with furosemide, spironolactone, or ACE in heart failure patients

Question 16

Side effects of Inodilators

Answer 16

Less arrhythmogenic than digitalis but may cause diarrhea, vomiting, inappetence, seizures, and polyuria/polydipsia

Question 17

Contraindications of Inodilators

Answer 17

Should not be used in hypertrophic cardiomyopathy

Clinical conditions where an increase in cardiac output is not physically possible

Question 18

Pharmacokinetics of Inodilators

Answer 18

Absorbed readily upon oral ingestion and around 60% bioavailability
Metabolically activated in the liver
Metabolites are excreted in feces
Bound to plasma proteins

Question 19

Vasodilator drugs

Answer 19

ACE inhibitors
Hydralazine
Nitrates - Sodium nitroprusside, Nitroglycerin, Isosorbide dinitrate
Prazosin

Question 20

Vasodilators

-ACE inhibitors

Answer 20

Captopril, Enalapril, Lisinopril, Benazepril
Angiotensin converting enzyme inhibitors
Vasodilators that also block the RAAS
Blocks conversion of Angiotensin I to Angiotensin II which is a vasoconstrictor

Question 21

Diuretics

-types and drugs

Answer 21

Loop diuretics - Furosemide
Thiazide diuretics - Hydrochlorothiazide, Chlorothiazide
Potassium-sparing diuretics - spironolactone, Triamterene, Amiloride

Question 22

Beta-blocker drugs

Answer 22

Carvedilol

Metoprolol or Atenolol

Question 23

MOA of Carvedilol

Answer 23

Nonselective Beta-blocker and alpha-1 blocker
Antioxidant
Inhibits endothelin (ET) release
           (peptides that constrict blood vessels and raise BP)

Question 24

Use of Carvedilol

Answer 24

Beta-blocker
In early treatment of CHF due to dilated cardiomyopathy to blunt the harmful effects of the sympathetic nervous system to the heart