- On 21 Dec 2000 at 10:21:00, Ken Ilett (kilett.-at-.receptor.pharm.uwa.edu.au) sent the message

Back to the Top

The following message was posted to: PharmPK

We have just completed a paper using P-Pharm and I have one question

about the correct description of the methods we have used. The relevant

section of the text is as follows:

Compartmental models (1 or 2) were fitted to the plasma

concentration-time data and analyzed using a population pharmacokinetic

approach implemented in the program P-Pharm Version 1.5 (InnaPhase,

France). A heteroscedastic error variance (1/Y2) model was used to

describe residual error and a log normal distribution were used to

describe inter-patient variability in clearance (CL), volume of

distribution (V) and absorption rate constant (ka). Bioavailability was

assumed to be unity.

My question is:

With respect to heoeroscedastic error variance using theY squared option

- should it be written as (*Y2) or (1/Y2) or what ???? - On 21 Dec 2000 at 19:09:18, "Xiaofeng Wang" (xwang.-at-.innaphase.com) sent the message

Back to the Top

The following message was posted to: PharmPK

Wheather it should be Y^2 or 1/Y^2 dependending on how the objective fuction

was expressed. For example,

if the objective function is expressed as

F = Sum of (Yobs(i)-Ypred(i))Wi +..., then Wi=1/Y^2; (1)

or F = Sum of (Yobs(i)-Ypred(i))/Wi + ..., then Wi=Y^2. (2)

In both Kinetica and P-Pharm, the obj function is defined as expression (2).

Scientific Support

InnaPhase Cor.

Philadelphia

USA

Want to post a follow-up message on this topic? If this link does not work with your browser send a follow-up message to PharmPK@boomer.org with "Technical help with P-Pharm Licence # P95079" as the subject

PharmPK Discussion List Archive Index page

Copyright 1995-2010 David W. A. Bourne (david@boomer.org)