[Clinical study of the biological availability of lanatoside C and digoxin in long-term tests].

: The bioavailability of digoxin and lanatoside C from tablets and dragees and from solutions of the two substances has been investigated intraindividually in patients on maintenance therapy. Plasma levels and urinary excretion were analyzed by radioimmunoassay. Both plasma concentrations and urinary excretion were significantly higher after digoxin tablets (1.5+/-0.17 ng/ml; 0.15 mg/24 h) than after lanatoside C dragees (0.98+/-0.15 ng/ml; 0.1 mg/24 h). When equimolar solutions of both drugs, corresponding to 0.5 mg digoxin, were given, plasma concentrations and urinary excretion after digoxin (1.6+/-0.08 ng/ml; 0.14 mg/24 h) were again significantly higher than after lanatoside C (1.18+/-0.09 ng/ml; 0.1 mg/24 h). These results suggest that while the absorption of lanatoside C is lower than that of digoxin, it is better than has been generally assummed. The variability in the absorption of lanatoside C between patients is no greater than with digoxin.