This may be an obvious question, but for a NCA where I am estimating PK parameters for parent and metabolite, what dose should be entered in the dosing panel for the metabolite? Is it the dose of the parent drug or should it be left blank since no actual dose of metabolite was administered? I am interested in the CL/F of the metabolite, but unless I enter a dose, this parameter will not be generated. Thanks for any guidance you can provide.
That is a great question. The only way to enter the dose for the metabolite is if you know the fraction of parent drug that is converted to the metabolite. Unfortunately, that information is rarely available. Generally this makes it impossible to determine the CL and V of the metabolite following administration of only the parent drug. A separate experiment with administration of the metabolite is required. Hope that helps.
Thank you for your quick reply! You are correct, I do not have information about the fraction metabolized, so I will leave the dose blank in the NCA.