title: [The biological availability of digitoxin].
abstract: The bioavailability of digitoxin after a single dose of 0.5 mg was studied in 6 healthy volunteers by estimation of tmax, cmax, AUC und urinary excretion rate. After tablets, absorption was rapid, after dragées delayed. The mean t1/2 of digitoxin for i.v. administration was 9.5 +/- 0.9 days, for oral administration of tablets 7.4 +/- 0.5 days and for dragées 9.7 +/- 2.0 days. The cumulative recovery of glycosides in urine during the first 48 hours was higher after tablets than after i.v. administration. The shorter t1/2 of digitoxin after tablets compared with the longer t1/2 after gastric juice resistent dragées demonstrated the presence of a substantial extrahepatic "first pass"-effect by degradation of digitoxin before absorption. Such mechanism would partly explain the shorter t1/2 after digitoxin-tablets due to an increased elimination of splitting products. By extrapolation to t-infinite AUC and urinary excretion rates were not significantly different between various formulations. The mean absolute bioavailability of digitoxin-dragées amounted to 82-88 percent and the relative bioavailability of digitoxin-tablets to 84-93 percent.
mesh_terms: D000284:Administration, Oral; D001682:Biological Availability; D004073:Digitoxigenin; D004074:Digitoxin / Q000008:administration & dosage / Q000378:metabolism*; D004304:Dosage Forms; D006801:Humans; D007275:Injections, Intravenous
chemical_list: D004304:Dosage Forms; D004073:Digitoxigenin; D004074:Digitoxin
vernacular_title: Die biologische Verfügbarkeit von Digitoxin.