Availability of tritium from non-aqueous solutions of [1,2-3H]methyltestosterone, administered orally to rats

Abstract

Abstract The solvent-water distribution coefficients of 17α-methyltestosterone have been determined in selected alkanes, alkanols and alkane-alkanol blends. The oral availability of tritium from solutions of [3 H]methyltestosterone in these solvents and blends was studied in rats by measuring radioactivity in plasma, faeces and urine. Disappearance of radioactivity from the gut and biliary recirculation of 3 H were also examined. Variation of the solvent led to marked changes in the absorption of radioactivity, suggesting a possible method of varying bioavailability from soft gelatin capsules. Neither distribution coefficients nor tritium concentrations changed significantly from one homologue to another, but there was a marked difference when the alkane series was compared with the alkanol series. Blends of octane and octanol, together with the pure solvents, provided a suitable spread of distribution coefficients and tritium concentrations, but no simple relationship could be established between the two properties.