Digoxin

Question 1

Clinical use

Answer 1

CHF → ↑ contractility

Atrial fibrillation → ↓ conduction at AV node via ↑ in parasympathetic tone

Question 2

MOA

Answer 2

Direct inhibition of Na+/K+ ATPase
↓ Na+ gradient results in indirect inhibition of
Na+/Ca2+ exchanger/antiport

↑ [Ca2+]i → positive inotropy

Question 3

Toxicity

Answer 3

Blurry yellow vision
Cholinergic; nausea, vomiting, diarrhea
Fife-threatening arrhythmias; ↑ PR, ↓ QT, T-wave inversion
May ↑ increase K+ serum levels
Renal insufficiency ↑ digoxin toxicity
Hypokalemia ↑ digoxin toxicity; without K+, digoxin can bind to Na+/K+ ATPase; digoxin competes for excretion and competes for tissue-binding sites

Question 4

Antidote KLAM

Answer 4

Slowly normalize K+
Lidocaine
Digoxin Antibodies (anti-dig Fab fragments)
Mg2+