OK! we cannot calculate Vdss with dataset from extravascular dosing alone [PK / PD]

posted by yjlee168 Homepage – Kaohsiung, Taiwan, 2016-09-26 01:27 (2555 d 04:57 ago) – Posting: # 16674
Views: 15,585

Dear mittyri,

Thanks for your response. You are correct. Apparently Vdss cannot be calculated using NCA with BE dataset alone. In WNL manual of the old version (v5.3), it said: (quoted) "An estimate of the volume of distribution at steady state. Vss = MRTINF*Cl, where MRT = Mean Residence Time and CL= total body clearance. For steady-state date (a typo? data?), Vss = MRTINF*Clss. Not computed for model 200, as calculating MRT from oral data requires estimating Mean Input Time, which requires compartmental methods." about Vdss. It is easy to calculate Vdss with IV or IV infusion since MRTiv is ready to use. For extravascular dosing (po for example), MRTpo = MRTiv + MITpo. Thus we not only require MIT (ka and tlag) but also MRTiv to calculate Vdss. BTW, I just find this R package PKNCA seems interesting. It calculates Vdss too.

Finally, I have a question: when using NCA to analyze a BE dataset, we can obtain MRT. Apparently this MRT is not what we call MRTpo. What is it?

All the best,
-- Yung-jin Lee
bear v2.9.1:- created by Hsin-ya Lee & Yung-jin Lee
Kaohsiung, Taiwan https://www.pkpd168.com/bear
Download link (updated) -> here

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