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RE: How to calculate t1/2, z?

From: Samtani, Mahesh [PRDUS] <MSamtani>
Date: Mon, 22 Feb 2010 16:05:58 -0500


There is an Excel spread sheet convert.xls for doing this, developed by
Dr. Steven Shafer. Please see this NMusers posting to download the
spread sheet (Terminal half-life will be 0.693 divided by the slowest
lambda rate constant from the excel spread-sheet):


Best wishes,



From: owner-nmusers
On Behalf Of Serge Guzy
Sent: Monday, February 22, 2010 3:20 PM
To: Li Y. Chen ; nmusers
Subject: RE: [NMusers] How to calculate t1/2, z?


Dear Li

I do not know if it will help you but here is a set of equations that
may be useful for you.


The initial parameterization I am using for the 3 compartment model with
first order absorption are different than yours but are sometimes
necessary to insure identifiability:



            CL,V2,V3,V4,Q3,DK42 and DKA


Then the series of equations 9already coded in Fortran) allow you to
estimate alpha, beta and gamma. I guess that the half-life you are
talking about would be Ln(2)/Gamma





c to be consistent with the regular 3 compt model, we define





c to be consistent with the regular 3 compt model, we define







c to be consistent with the regular 3 compt model, we define




























c TX=DACOS( (-BX/2D0)/DSQRT(-AX*AX*AX/27D0) )










C Terminal half-life




Best Regards;

Serge Guzy;Ph.d

President, CEO; POP_PHARM





From: owner-nmusers
On Behalf Of Li Y. Chen
Sent: Monday, February 22, 2010 8:17 AM
To: nmusers
Subject: [NMusers] How to calculate t1/2, z?


I have a three-compartment model. Dose anyone know how to calculate the
terminal half life (t1/2, Z) using the finial estimates (V2, V3, V4,
CL2, CL3, and CL4)?

t1/2, z= ln2*Varea/CL, should Varea =V2+V3+V4? How about CL?

Thank you!




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Received on Mon Feb 22 2010 - 16:05:58 EST

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