• Clinical science

Cardiac glycosides (Digitalis…)

Abstract

Cardiac glycosides are drugs that inhibit the Na+/K+- ATPases found on the outer cell surface. Digoxin is the only drug of this class that is commonly used in clinical settings. The main indications for digoxin treatment are atrial fibrillation and heart failure in treatment-resistent cases. Because cardiac glycosides have a narrow therapeutic index, close monitoring of serum concentrations is necessary. Typical symptoms of cardiac glycoside poisoning are nausea, vomiting, blurry vision, and cardiac arrhythmias. Overdose can quickly become life-threatening and swift treatment is vital. The first-line treatment for cardiac glycoside poisoning is administration of digoxin-specific antibodies.

Overview

  • Mechanism: inhibition of the cardiac and neuronal Na+/K+- ATPases
  • Onset of effect:
    • Oral: 0.5–2 h
    • IV: 15–30 min
  • Half-life: 36–40 hours
  • Hydrophilic
  • 20–40% protein bound
  • Renal elimination

References:[1][2][3][4][5][6]

Effects

  • Inhibition of Na+/K+-ATPases → higher intracellular Na+ concentration → reduced efficacy of Na+/Ca2+ exchangershigher intracellular Ca2+ concentration → increased vagal tone

Cardiac glycosides inhibit Na+/K+-ATPase, increasing cardiac contractility and decreasing AV conduction and heart rate!

Cardiac glycoside poisoning

Digoxin has a narrow therapeutic index! Serum concentrations of cardiac glycosides must be monitored closely because overdoses can have severe consequences!

References:[1][3][7][5][6]

Indications

References:[4][8]

Contraindications

References:[7][8]

We list the most important contraindications. The selection is not exhaustive.

Interactions

References:[9]