Related Experiment Video
Updated: Oct 17, 2026

Mass Spectrometry and Luminogenic-based Approaches to Characterize Phase I Metabolic Competency of In Vitro Cell Cultures
Published on: March 28, 2017
14C-isomazole disposition in man after oral administration
J R Woodworth1, A F DeLong, A F Fasola
1Lilly Laboratory for Clinical Research, Wishard Memorial Hospital, Indianapolis, Indiana 46202.
Abstract:
A 50-mg dose containing 50 microCi 14C-isomazole was administered orally to five healthy male volunteers. Blood, plasma, urine, feces, and saliva were collected and measured for total 14C; in addition, all collections except feces were measured for parent drug (ISO) and three metabolites: hydroxyisomazole (OHISO) and sulfone (SULF) and hydroxysulfone (OHSULF) analogues. Urine and fecal recoveries accounted for 97.0% of the drug administered, with 62.6% excreted in urine and 32.4% in feces. Only 47% of the drug recovered in urine could be identified, with ISO the largest constituent. Total plasma 14C peaked at 1.5 hr, indicating rapid absorption, and produced a mean half-life of 3.7 hr. This was similar to the total 14C half-life found in blood (3.1 hr) but longer than in red blood cells (1.8 hr) or saliva (1.4 hr), suggesting that different ISO-related compounds contributed to the results found in each fluid or tissue. An unidentified metabolite(s) composed a large portion of circulating plasma 14C and produced the longer half-life encountered in plasma. ISO exhibited a short half-life (1.35 hr), a high oral clearance (Cls/F; 24.2 ml/min/kg), and some extravascular distribution (V beta; 3.07 L/kg). Total 14C in red blood cells and saliva related very well to plasma ISO disposition, suggesting preferential distribution of parent drug across cellular membranes. The estimated RBC:plasma ISO ratio (1.79) confirmed this hypothesis. Saliva may be used as a noninvasive means to monitor ISO disposition.
More Related Videos
Related Concept Videos
First Pass Effect
Depending on the route of administration, drugs can be metabolized in the liver, intestine, lungs, and vasculature. Orally administered drugs are first absorbed through the...
Drug Excretion: Miscellaneous Routes
Dosage Regimens: Partial Pharmacokinetic Parameters
Dosage Regimen: Multiple Oral Dosage
IV Infusion to Oral Dosing: Conversion Methods
Pharmacokinetic–Pharmacodynamic Relationship: Duration of Dose-Effect Relationship

![Radiosynthesis of 1-(2-[18F]Fluoroethyl)-L-Tryptophan using a One-pot, Two-step Protocol](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F63025.jpg&w=3840&q=50)