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Pharmacokinetics Absorption Following oral administration, peak serum concentrations of digoxin occur at 1 to 3 hours. Absorption of digoxin from digoxin tablets has been demonstrated to be 60% to 80% complete compared to an identical intravenous dose of digoxin (absolute bioavailability) or Digoxin Solution in Capsules (relative bioavailability). Text Continues Below
When digoxin tablets are taken after meals, the rate of absorption is slowed, but the total amount of digoxin absorbed is usu-ally unchanged. When taken with meals high in bran fiber, however, the amount absorbed from an oral dose may be reduced. Comparisons of the systemic availability and equivalent doses for oral preparations of digoxin are shown in Table 1: Table 1: Comparisons of the Systemic Availability and Equivalent Doses for Oral Preparations of Digoxin
*For example, 125-mcg Digoxin Tablets equivalent to 125 mcg Di-goxin Pediatric Elixir equivalent to 100 mcg Digoxin Solution in Capsules equivalent to 100 mcg Digoxin Injection/ IV. In some patients, orally administered digoxin is converted to inac-tive reduction products (e. g., dihydrodigoxin) by colonic bacteria in the gut. Data suggest that one in ten patients treated with digoxin tablets will degrade 40% or more of the ingested dose. As a result, certain antibiotics may increase the absorption of digoxin in such patients. Although inactivation of these bacteria by antibiotics is rapid, the serum digoxin concentration will rise at a rate consistent with the elimination half-life of digoxin. The magnitude of rise in serum digoxin concentration relates to the extent of bacterial inacti-vation, and may be as much as two-fold in some cases. Distribution Following drug administration, a 6-to 8-hour tissue distribution phase is observed. This is followed by a much more grad-ual decline in the serum concentration of the drug, which is depend-ent on the elimination of digoxin from the body. The peak height and slope of the early portion (absorption/ distribution phases) of the serum concentration-time curve are dependent upon the route of administration and the absorption characteristics of the formulation. Page: << Prev | 1 | 2 | 3 | 4 | 5 | Next >>
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