From: Samtani, Mahesh [PRDUS] <*MSamtani*>

Date: Mon, 22 Feb 2010 16:05:58 -0500

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

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

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: 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!

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

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the individual sender, except where the message states otherwise and the

sender is authorized to state them to be the views of XOMA.

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

Date: Mon, 22 Feb 2010 16:05:58 -0500

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

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

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: 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!

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.

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