Bioequivalence and Bioavailability Forum • OK! we cannot calculate Vdss with dataset from extravascular dosing alone

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

posted by yjlee168 – Kaohsiung, Taiwan, 2016-09-26 01:27 (3554 d 21:37 ago) – Posting: # 16674
Views: 22,753

Dear mittyri,

Thanks for your response. You are correct. Apparently Vd_ss 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 Vd_ss. It is easy to calculate Vd_ss with IV or IV infusion since MRT_iv is ready to use. For extravascular dosing (po for example), MRT_po = MRT_iv + MIT_po. Thus we not only require MIT (k_a and t_lag) but also MRT_iv to calculate Vd_ss. BTW, I just find this R package PKNCA seems interesting. It calculates Vd_ss 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 MRT_po. What is it?

—
All the best,
-- Yung-jin Lee
bear v2.9.6:- created by Hsin-ya Lee & Yung-jin Lee
Kaohsiung, Taiwan https://www.pkpd168.com/bear
Download link (updated) -> here

Complete thread:

volume of distribution at steady state martin 2011-10-18 07:49
- Vss d_labes 2011-10-18 11:36
  - History Helmut 2011-10-18 16:02
    - History javier 2016-09-21 16:47
      - Amazon? Yes. yjlee168 2016-09-22 11:30
        
        Gold Letters d_labes 2016-09-22 12:09
        
        Gold Letters yjlee168 2016-09-24 20:26
        
        Another quest mittyri 2016-09-25 15:04
        
        TopFit: 16bit DOS-application Helmut 2016-09-25 23:41
        
        TopFit: less than 1.44 MB mittyri 2016-09-26 00:02
        
        TopFit: less than 1.44 MB Helmut 2016-09-26 00:17
        
        TopFit: less than 1.44 MB ElMaestro 2016-09-26 09:43
        
        TopFit: 16bit DOS-application yjlee168 2016-09-26 00:18
- volume of distribution at steady state ElMaestro 2016-09-23 23:13
  - Vss: MIT is needed anyway... mittyri 2016-09-24 00:38
    - it seems possible for me... yjlee168 2016-09-24 20:19
      - Leslie disagrees mittyri 2016-09-24 21:33
        
        OK! we cannot calculate Vdss with dataset from extravascular dosing aloneyjlee168 2016-09-25 23:27
        
        MRTINF includes Mean Input Time mittyri 2016-09-25 23:45
        “Gravity Duration” Helmut 2016-09-25 23:47
    - Was Leslie wrong about Eq (8)? yjlee168 2016-09-26 00:13
      - Leslie cannot be wrong mittyri 2016-09-26 00:23