Cardiac glycosides and others drugs for CHF

Question 1

Prototype cardiac glycosides

Answer 1

digoxin

Question 2

Therapeutic effect of digoxin

Answer 2

positive inotropic effect, increases force

Question 3

MOA of digoxin

Answer 3

direct- inhibits Na+/K+ ATPase which decreases Na+/Ca++ and increase intracellular Ca++ allows heart to beat more forcefully
indirect- parasympathomimetic

Question 4

Contraindication of digoxin

Answer 4

worsens ventricular tachycardia because digoxigen acts on ventricular tissue to decrease refractory period and increase conduction velocity

Question 5

Pharmacokinetics of digoxin

Answer 5

40 hour half life, for quick action need a loading dose. Can be degraded by intestinal bacteria, interaction with antibiotics.

Question 6

Toxicity of digoxin

Answer 6

toxicity is only 3 fold greater than therapeutic dose
toxicity is usually due to K+ depletion combined with digoxin therapy, low K+ increases binding to Na+/K+ exchanger
Can lead to ventricular tachycardia and fibrillation

Question 7

Side effects of digoxin

Answer 7

GI, CNS, visual effects, Male breast enlargement

Question 8

Treatment of digitalis toxicity

Answer 8

Monitor ECG, adjust K+ levels, lidocaine for ventricular arrhythmias, emergency: Digibind

Question 9

Drug interactions with digoxin

Answer 9

K+ depleting diuretics, quinidine increases plasma concentrations, antibiotics can decrease metabolism

Question 10

Other drugs used in heart failure (6)

Answer 10

Diuretics
Ace inhibitors
Beta blockers
angiotensin receptor antagonists
Aldosterone antagonists
vasodilators

Question 11

Cardiac toxicity of digoxin

Answer 11

1. premature ventricular beat
2. ventricular tachycardia and fibrillation
3. AV junctional rhythm
4. AV block