TY - JOUR T1 - Disposition and Metabolism of Rifapentine, a Rifamycin Antibiotic, in Mice, Rats, and Monkeys JF - Drug Metabolism and Disposition JO - Drug Metab Dispos SP - 725 LP - 731 VL - 26 IS - 8 AU - W. Bart Emary AU - Paul C. Toren AU - Brad Mathews AU - Kay Huh Y1 - 1998/08/01 UR - http://dmd.aspetjournals.org/content/26/8/725.abstract N2 - Rifapentine is a cyclopentyl derivative of rifampin under development for the treatment of Mycobacterium tuberculosisand Mycobacterium avium complex infections. These studies were designed to investigate the disposition and biotransformation of single iv and oral doses of 14C-rifapentine in mice, bile duct–cannulated and uncannulated rats, and monkeys. Mass balance studies included 14C analyses of urine, feces, bile, cage wash, carcasses, and cage air collected for up to 120 hr postdose. Separation of radioactive compounds extracted from urine, bile, and feces was conducted using high-performance liquid chromatography and radioisotope detection. The mass spectra of selected chromatographic peaks were obtained. Disposition results were similar for all three species. Less than 5% of the radioactive dose of14C-rifapentine was recovered in urine, indicating that renal excretion is a minor route of elimination in these species. The major route of elimination of radioactivity was into the feces, where more than 75% of the radioactivity was recovered. Biliary excretion was the major route of elimination of radioactivity in bile duct-cannulated rats dosed either po or IV. Radiochromatograms were similar for fecal samples from animals dosed by IV or orally. Ten regions of radioactivity were observed in mouse and rat fecal sample radiochromatograms, and seven regions of radioactivity were observed in monkey fecal sample radiochromatograms. The most abundant compound identified in feces was usually intact rifapentine (27%–41% of dose in mouse, 3%–35% of dose in rat, and 17%–29% of dose in monkey). Other peaks identified or characterized in feces based on liquid chromatography/ultraviolet/14C and/or liquid chromatography/mass spectrometry methods included 25-desacetyl-rifapentine, 3-formyl-25-desacetyl-rifapentine, and 3-formyl-rifapentine. The compounds rifapentine, 25-desacetyl-rifapentine, and 3-formyl-rifapentine were present in rat bile samples. These studies show that the metabolism and disposition of rifapentine in mice, rats, and monkeys were similar. The American Society for Pharmacology and Experimental Therapeutics ER -