Jump to content


Photo

Vss question


  • Please log in to reply
2 replies to this topic

#1 Goodmans

Goodmans

    Newbie

  • Members
  • Pip
  • 1 posts

Posted 28 September 2018 - 10:21 AM

Hi all. 

 

I have a question regarding Volume of distribution at steady state, Vss.

 

My understanding is that Vss is measured at the phase of the profile in which drug is at steady state between central and peripheral compartments – i.e. drug leaves the central compartment at the same rate at which it enters the central compartment from peripheral compartment(s). 

 

If my understanding is correct (which it may not be), then why is it that WinNonlin will only produce a value for Vss using AUCtau and not AUC0-t? The fact that it only uses AUCtau implies that Vss is only relevant following repeat dosing and that steady state may actually refer to steady state following repeat dosing.  Does this mean that in a repeat dose study, I should not report Vss following a single, first dose?

 

I would be very grateful for any clarification on this, and any corrections to my assumptions.

 



#2 Simon Davis

Simon Davis

    Advanced Member

  • Administrators
  • 1,316 posts

Posted 28 September 2018 - 12:41 PM

I think the NCA theory is that Vss can only be estimated with confidence at steady-state obtained after repeat dosing.

 

 Simon.



#3 Linda Hughes

Linda Hughes

    Advanced Member

  • Members
  • PipPipPip
  • 73 posts

Posted 30 September 2018 - 12:46 PM

For your question about Vss following a single first dose, the definition of Vss is in terms of MRTINF, but MRTINF is defined differently for single-dose versus steady-state.  The single-dose definition does not depend on AUCTAU.

The parameter definitions for single-dose and steady-state are given in the WinNonlin Users Guide in the last section of the NCA chapter.

 

Regards,

Linda Hughes






0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users