Name: Digitoxin (Crystodigin)
Class: CHF Rx (Cardiac Glycoside)
Mechanism: Inhib. of Na+/K+ ATPase ® release of Ca2+ from SR ® myocardial contractility. Also sensitivity of AV node to vagal stimulation ® ¯ ventricular rate in atrial flutter or fibrillation (i.e., anti-arrhythmic).
Absorption:
Dist.: Strong protein binding.
Metabolism.: Hepatic Metabolism.
Excretion, t½: Feces. Longer t½ than digoxin.
Toxicity/S.E.s: Low therapeutic index. Toxicity enhanced by hypokalemia. Arrhythmias (possibly life-threatening), anorexia, n/v/d, drowsiness, fatigue, visual disturbances. Verapamil or quinidine ® toxicity.
Utility: Treat heart failure.
Special Features: Active Metabolismolites. Longer t½, more GI absorption, and more protein binding than digoxin.