14C-Nifedipine suppository was administered intrarectally (i.r.) in rat, in order to investigate its absorption, distribution, metabolism and excretion, comparing with the data after i.v. or oral administration of 14C nifedipine solutionAlso the metabolic fate was investigated after daily dosing of 14C-nifedipine suppository.After i.v. administration, the level of radioactivity in the blood decreased biphasically, with the corresponding half-lives of 1.0h and 38.5h, resp.The maximum concentration of radioactivity in the blood at 45 min after i.r. administration was higher than that observed after oral application.The excretion ratio of radioactivity in the urine and feces was similar among those 96 h after i.r., i.v. and oral administration; 51∼53 and 46∼41% of dose in the urine and feces, resp.The distribution of radioactivity in tissues after i.r. administration was similar to that of oral administration except that in gastrointestinal tract.At 45 min after i.r. administration, the tissue levels of radioactivity were higher in the liver, kidney and plasma than blood, and very low in brain.Metabolites in the plasma and urine after 3 different administration routes were similar.Unchanges 14C-Nifedipine was found in plasma at the early period after administration, but not in urine.During the repeated intrarectal administration, the level of radioactivity in the blood at 24 h after daily dosing continued to increase till the 7th day, then reached to the plateau.The excretion rates of radioactivity in the urine and feces were nearly constant during the period of repeats, and were similar to those after a single administration.The tissue levels of radioactivity appeared not to be accumulated in the tissues.
