New information regarding digitalis metabolism.

The digitalis glycosides, digoxin and digitoxin, have been examined in the light of new information regarding absorption, excretion, and metabolism. Digitoxin is completely absorbed, extensively recycled in the intestine, protein-bound, metabolized, and excreted largely in the urine as metabolites. It possesses, as a result, a long half-time of five to seven days. Factors governing its excretion and metabolism are incompletely studied in human subjects. Digoxin is 80 percent to 90 percent absorbed, little recycled, relatively little protein-bound, relatively little metabolized, and excreted largely unchanged in the urine. As a result it has a shorter half-time of 1.5 days and its excretion may be directly related to creatinine clearance. These properties of the commonly used glycosides should assist in clinical management of patients with congestive heart failure. Smaller doses of either glycoside than usually prescribed appear to suffice for adequate digitalization, and the dangerous complication of digitalis toxicity may then be avoided.