Fraction of metabolite formation

Hello All, I am working with PK profiles of parent and active metabolite. Parent drug was administered orally and has two metabolites (active and in active). I am looking for the most efficient way to understand the fraction of active metabolite formed when a parent drug is administered orally. Any help would be greatly appreciated. Thanks & Regards *Saikumar Matcha* *p: +1 9199045716*

Dear Saikumar, With only data following administration of the parent drug (independent of route of administration) it is not feasible to assess the fraction of different metabolites formed. In order to do so you need more information. The best form of information comes from intravenous administration of the respective metabolites of interest as well as the parent drug. In the absence of direct access to such data the only other option comes from utilizing prior literature data and/or mechanistic predictions based on translational techniques (QSAR, IVIVC, physiological scaling from animals etc.). You can still model the parent-metabolite(s) data in a way that describes the plasma concentrations of each respective moiety over time i.e. without knowing the absolute fraction that forms each metabolite. This has been discussed in this forum previously, see for example this thread: https://www.mail-archive.com/[email protected]/msg03964.html Kind regards, Martin Bergstrand, Ph.D. Principal Consultant Pharmetheus AB www.pharmetheus.com