RE: Fx

From: Paul Hutson prhutson@pharmacy.wisc.edu Subject: RE: [NMusers] Fx Date: Tue, May 25, 2004 12:47 pm Dear Katya, Nick and Bill: Let us assume another case to test my understanding of your explanation. Let us assume an orally administered controlled release system... F1 would represent the bioavailability of the nominal dose of the product that was delivered to the lumen of the gut.(yes?) Let us assume the fraction released is 0.6 A fraction of this released, intraluminal drug is then absorbed into the systemic circulation (let's ignore about first pass). Let us assume that the fraction of intraluminal drug absorbed is 0.7. I would normally consider F2 to be 0.7, however from your explanations, F2 would appear to be 0.6 x 0.7 = 0.42. (The relative amount of the dose (AMT) that enters systemic circulation, CMT2). In a sense, the contribution of F1 is hidden, which is typically the case in evaluating the relative bioavailability of different products, in difference subjects. However, if I could collect the oral dosage delivery device :-( and determine the residual drug for that dose in that patient, I would then know by difference the F1. Hence, my interest in whether F2 is specifically the overall fraction of AMT that enters CMT2, or whether it is the fraction of the amount in the CMT1 depot compartment (AMT*F1) that enters CMT2. It strikes me than another example of this being relevant is in an animal model with simultaneous sampling of the portal and hepatic veins modeling the Fx associated with hepatic extraction. Thanks! Paul Paul Hutson, Pharm.D. Associate Professor (CHS) UW School of Pharmacy 777 Highland Avenue Madison, WI 53705-2222 Tel: (608) 263-2496 FAX: (608) 265-5421 Pager: (608) 265-7000, #7856