Digoxin
- Class: Na+/K+-ATPase inhibitor
- Used for: a weak heartbeat
- Say it: dih-JOX-in
- Forms: tablet, oral liquid, injection
DIGOXIN tells the tiring heart to DIG IN and pull harder with every squeeze.
Blocking the sodium-potassium pump raises calcium inside the heart muscle cell, so each contraction is stronger. It digs in rather than speeding up.
Jamming the Na+/K+ pump indirectly raises calcium inside the heart cell, so each beat is stronger. Low potassium lets digoxin bind more tightly — which is how a diuretic causes digoxin toxicity.
Side effects
Common: nausea, loss of appetite, dizziness
Serious: arrhythmia, yellow-green vision
Typical dose
125–250 micrograms once daily
Micrograms, not milligrams. The narrow margin makes level checks and potassium monitoring essential — low potassium makes toxicity far more likely.
Check yourself
A patient on digoxin and furosemide has nausea and yellow-green vision. What is the most likely cause?
- Digoxin toxicity brought on by a low potassium
- An allergic reaction to furosemide
- Worsening heart failure
- Developing cataracts
Show answer
A. Digoxin toxicity brought on by a low potassium
Potassium and digoxin compete for the same site on the pump. When potassium falls, digoxin binds more, so a dose that was safe last month becomes toxic — the classic diuretic-plus-digoxin trap.
See it, don't memorize it
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