JAMES E. DOHERTY, M.D., F.A.C.P.
Digoxin is 75% to 85% absorbed when administered orally; little is metabolized, and it is excreted in the urine principally unchanged. Optimum digoxin serum levels are 0.5 to 2.5 ng/ml; more than 3.0 ng is almost always a toxic level in adults. The half-life of digoxin is 34 hours. Digitoxin is 100% absorbed when taken orally; it is extensively metabolized and excreted in stool and urine principally as cardioinactive metabolities. Optimum serum levels are 20 to 35 ng/ml, and toxicity is usually associated with a level of 45 ng/ml or more. The half-life of digitoxin is 5 to 7 days. Lack of biologic availability sometimes necessitates large doses of the glycosides. Biologic availability can be evaluated with serum glycoside measurements. Knowledge of the patient's age, thyroid and renal function, and electrolyte balance will help to determine the appropriate dose of glycoside. Smaller glycoside doses are generally recommended, particularly for digoxin, which is better absorbed than previously supposed.
DOHERTY JE. Digitalis Glycosides: Pharmacokinetics and Their Clinical Implications. Ann Intern Med. ;79:229–238. doi: 10.7326/0003-4819-79-2-229
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Published: Ann Intern Med. 1973;79(2):229-238.
Emergency Medicine, Endocrine and Metabolism, Hospital Medicine, Thyroid Disorders.
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