title: Comparison between Radioanalysis and19F Nuclear Magnetic Resonance Spectroscopy in the Determination of Mass Balance, Metabolism, and Distribution of Pefloxacin.
abstract: Mass balance and metabolism studies using radiolabeled substances are well recognized as an important part of the drug development process. In this study, we directly assessed the use of fluorine nuclear magnetic resonance (19F NMR) to achieve quantitative mass balance, metabolism, and distribution information for fluorinated compounds, without the need for radiolabeled synthesis or study. As a test case, the disposition of pefloxacin, a fluoroquinolone antibiotic, was evaluated in rats using quantitative19F NMR in parallel with a radiolabeled study. Urine, bile, and feces samples were collected over specific periods after oral administration of either 25 mg/kg [14C]pefloxacin or 25 mg/kg pefloxacin and were subsequently profiled by radioactivity or19F NMR, respectively. The percentage of dose excreted in each matrix was comparable between the two methods, with the total dose recovered by radioactivity and19F NMR determined to be 86.8% and 81.8%, respectively. In addition, plasma samples were collected to determine the exposure of pefloxacin and its circulating metabolites. The plasma exposure of pefloxacin determined by19F NMR was within 5% to that calculated by a validated liquid chromatography-tandem mass spectrometry bioanalytical method. By both methods, pefloxacin was identified as the major circulating entity, with pefloxacin glucuronide as the major circulating metabolite. Quantitative analysis of metabolites in excreta was generally comparable between the two methods. In selected tissues, both methods indicated that the parent drug accounted for most of the drug-related material. In summary, we have demonstrated that19F NMR can be used as an alternative method to conventional radiolabeled studies for compounds containing fluorine without the need for radiolabeled synthesis/study.
authors.affiliation: Analytical Technologies (H.H.) and Drug Disposition (K.K., B.A.C., E.J.P., P.K.), Lilly Research Laboratories, Indianapolis, Indiana.
authors.forename: Haitao
authors.initials: H
authors.lastname: Hu
authors.affiliation: Analytical Technologies (H.H.) and Drug Disposition (K.K., B.A.C., E.J.P., P.K.), Lilly Research Laboratories, Indianapolis, Indiana.
authors.forename: Kishore Kumar
authors.initials: KK
authors.lastname: Katyayan
authors.affiliation: Analytical Technologies (H.H.) and Drug Disposition (K.K., B.A.C., E.J.P., P.K.), Lilly Research Laboratories, Indianapolis, Indiana.
authors.forename: Boris A
authors.initials: BA
authors.lastname: Czeskis
authors.affiliation: Analytical Technologies (H.H.) and Drug Disposition (K.K., B.A.C., E.J.P., P.K.), Lilly Research Laboratories, Indianapolis, Indiana.
authors.forename: Everett J
authors.initials: EJ
authors.lastname: Perkins
authors.affiliation: Analytical Technologies (H.H.) and Drug Disposition (K.K., B.A.C., E.J.P., P.K.), Lilly Research Laboratories, Indianapolis, Indiana pkulanthaivel@lilly.com.
authors.forename: Palaniappan
authors.initials: P
authors.lastname: Kulanthaivel
mesh_terms: D000284:Administration, Oral; D000818:Animals; D000900:Anti-Bacterial Agents / Q000032:analysis / Q000737:chemistry / Q000493:pharmacokinetics*; D001646:Bile / Q000737:chemistry; D002250:Carbon Radioisotopes / Q000032:analysis* / Q000737:chemistry; D002853:Chromatography, Liquid; D005243:Feces / Q000737:chemistry; D005461:Fluorine / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D015366:Pefloxacin / Q000032:analysis / Q000737:chemistry / Q000493:pharmacokinetics*; D051381:Rats; D017207:Rats, Sprague-Dawley; D053719:Tandem Mass Spectrometry
chemical_list: D000900:Anti-Bacterial Agents; D002250:Carbon Radioisotopes; D005461:Fluorine; D015366:Pefloxacin