[Pharmacokinetics of digitoxin in chronic renal failure (author's transl)]

Digitoxin concentration, measured by radio-immunoassay, was significantly lower in 51 patients in chronic renal failure (23.2 +/- 7.8 mug/l) than in 29 patients in heart failure (26.5 +/- 7.3 mug/l), although both groups were on the same maintenance dose of 0.1 mg daily. Despite a normal serum albumin concentration, digitoxin protein binding was less in uraemic patients than in those with normal renal function. Renal failure did not affect intestinal digitoxin absorption. In patients in chronic renal failure elimination half-time was significantly shorter (5.7 +/- 0.9 days) than in healthy controls (7.6 +/- 1.6 days). There was no significant difference in the excretion of water-soluble ("cardioinactive") digitoxin metabolites in urine between patients in chronic renal and those in heart failure. In patients with normal renal function, of dichloromethane-soluble (cardioactive) metabolites only digitoxin could be demonstrated by thin-layer chromatography. The results indicate that patients in chronic renal failure can safely be given the same dose as those with normal renal function, without danger of over- or underdosage.