parent drug & metabolite

From: "Gerard Box" <pkpd@hotmail.com> Subject: parent drug & metabolite Date: Mon, 23 Apr 2001 22:59:05 -0000 Dear nmusers, I would like to characterise the pk of parent drug and metabolite in the same run. A single oral dose of the parent compound is administered to healthy volunteers and parent drug + metabolite are sampled in blood. In the NONMEM input file, dosing of parent compound following oral administration is in compartment 1, whereas blood concentrations of both parent drug and metabolite are in compartment 2. How does one define the input row for the metabolite, since it is not actually administered? Is it a fraction F of the dose in compartment 1 or are there other tricks to solve this problem? Kind regards, Gerard