| Abstrakt: |
A commercial digitoxin radioimmunoassay procedure, normally used to evaluate equilibrium-state plasma levels, was modified such that the sensitivity was increased 20-fold. Due to the extensive metabolism of digitoxin in man, the specificity of the assay procedure for digitoxin was determined against several known metabolites. These studies indicated that the assay procedure was more sensitive to digoxin and the monodigitoxoside and bisdigitoxoside of digitoxigenin than to digitoxin itself. It also had a lesser degree of sensitivity to the aglycone digitoxigenin. For the bioavailability study, single 0.1-mg. doses of digitoxin were administered orally, as one of two commercial brands of tablets, to a panel of eight subjects in a crossover study with 56 days separating the two doses. Plasma levels were measured for 15 days following dosing. Significant differences in the plasma levels between brands, as determined by analysis of variance, were found at 0.5, 1, 72, and 240 hr. The peak plasma levels were found to differ significantly. No statistical difference in the relative bioavailability, as measured by the area under the plasma level curve, was found between the two tablets tested. |
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