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!
Li
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
K10=CL/V2
K23=Q3/V2
c to be consistent with the regular 3 compt model, we define
k12=k23
K32=Q3/V3
c to be consistent with the regular 3 compt model, we define
k21=k32
K42=K32+DK42
c to be consistent with the regular 3 compt model, we define
k31=k42
Q4=K42*V4
K24=Q4/V2
EX2=K23+K24+K10
EX3=K32
EX4=K42
PX=EX2+EX3+EX4
QX=EX2*EX3+EX2*EX4+EX3*EX4-K23*K32-K24*K42
RX=EX2*EX3*EX4-K23*K32*EX4-K24*K42*EX3
AX=(3D0*QX-PX*PX)/3D0
BX=(2D0*PX*PX*PX-9D0*PX*QX+27D0*RX)/27D0
TERM1=(-BX/2D0)/DSQRT(-AX*AX*AX/27D0)
C WE AVOID VALUES <-1 AND >1
IF(TERM1.LT.-1.)THEN
TERM1=-0.999
ENDIF
IF(TERM1.GT.1.)THEN
TERM1=0.999
ENDIF
c TX=DACOS( (-BX/2D0)/DSQRT(-AX*AX*AX/27D0) )
TX=DACOS(TERM1)
ALPH=PX/3D0-2D0*DSQRT(-AX/3D0)*DCOS(TX/3D0+2D0*PI/3D0)
alpha=ALPH
BETA=PX/3D0-2D0*DSQRT(-AX/3D0)*DCOS(TX/3D0+4D0*PI/3D0)
GMMA=PX/3D0-2D0*DSQRT(-AX/3D0)*DCOS(TX/3D0)
gamma=gmma
KA=ALPH+DKA
C Terminal half-life
Terminal_half_life=dlog(2)/gamma
Best Regards;
Serge Guzy;Ph.d
President, CEO; POP_PHARM
Quoted reply history
From: [email protected] [mailto:[email protected]]
On Behalf Of Li Y. Chen
Sent: Monday, February 22, 2010 8:17 AM
To: [email protected]
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!
Li
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Hello,
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):
http://cognigencorp.com/nonmem/nm/97aug142001.html
Best wishes,
MNS
Quoted reply history
From: [email protected] [mailto:[email protected]]
On Behalf Of Serge Guzy
Sent: Monday, February 22, 2010 3:20 PM
To: Li Y. Chen ; [email protected]
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
K10=CL/V2
K23=Q3/V2
c to be consistent with the regular 3 compt model, we define
k12=k23
K32=Q3/V3
c to be consistent with the regular 3 compt model, we define
k21=k32
K42=K32+DK42
c to be consistent with the regular 3 compt model, we define
k31=k42
Q4=K42*V4
K24=Q4/V2
EX2=K23+K24+K10
EX3=K32
EX4=K42
PX=EX2+EX3+EX4
QX=EX2*EX3+EX2*EX4+EX3*EX4-K23*K32-K24*K42
RX=EX2*EX3*EX4-K23*K32*EX4-K24*K42*EX3
AX=(3D0*QX-PX*PX)/3D0
BX=(2D0*PX*PX*PX-9D0*PX*QX+27D0*RX)/27D0
TERM1=(-BX/2D0)/DSQRT(-AX*AX*AX/27D0)
C WE AVOID VALUES <-1 AND >1
IF(TERM1.LT.-1.)THEN
TERM1=-0.999
ENDIF
IF(TERM1.GT.1.)THEN
TERM1=0.999
ENDIF
c TX=DACOS( (-BX/2D0)/DSQRT(-AX*AX*AX/27D0) )
TX=DACOS(TERM1)
ALPH=PX/3D0-2D0*DSQRT(-AX/3D0)*DCOS(TX/3D0+2D0*PI/3D0)
alpha=ALPH
BETA=PX/3D0-2D0*DSQRT(-AX/3D0)*DCOS(TX/3D0+4D0*PI/3D0)
GMMA=PX/3D0-2D0*DSQRT(-AX/3D0)*DCOS(TX/3D0)
gamma=gmma
KA=ALPH+DKA
C Terminal half-life
Terminal_half_life=dlog(2)/gamma
Best Regards;
Serge Guzy;Ph.d
President, CEO; POP_PHARM
From: [email protected] [mailto:[email protected]]
On Behalf Of Li Y. Chen
Sent: Monday, February 22, 2010 8:17 AM
To: [email protected]
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!
Li
________________________________
The information contained in this email message may contain confidential
or legally privileged information and is intended solely for the use of
the named recipient(s). No confidentiality or privilege is waived or
lost by any transmission error. If the reader of this message is not the
intended recipient, please immediately delete the e-mail and all copies
of it from your system, destroy any hard copies of it and notify the
sender either by telephone or return e-mail. Any direct or indirect use,
disclosure, distribution, printing, or copying of any part of this
message is prohibited. Any views expressed in this message are those of
the individual sender, except where the message states otherwise and the
sender is authorized to state them to be the views of XOMA.