- On 3 Apr 2002 at 16:54:26, "Rob Ariano" (RARIANO.at.sbgh.mb.ca) sent the message

Back to the Top

Hi all,

Does anyone have a formula which describes a steady-state

concentration-time profile from basic microconstants for a

2-compartment open model (ie. k10, k12, etc)? We need to simulate

concentrations at any time point after a steady-state dose. Is this

even possible (ie. something that can be computated within Excel, and

not with the use of a program, like ADAPT)?

Best regards,

Rob Ariano

Robert Ariano, Pharm.D.,BCPS

Clinical Pharmacist Critical Care

St.Boniface General Hospital; &

Associate Professor of Pharmacy,

& Medicine, University of Manitoba,

rariano.-at-.sbgh.mb.ca

www.sbgh.mb.ca - On 4 Apr 2002 at 12:17:37, David Bourne (david.-at-.boomer.org) sent the message

Back to the Top

[A few replies - db]

From: "David M. Foster"

Date: Thu, 4 Apr 2002 07:58:08 -0800

To: david.at.boomer.org

Subject: Re: PharmPK Formula for steady-state 2 compartment model

I think it may be possible with Excel, but programs such as ADAPT or SAAM II

(www.saam.com) do it quickly and easily.

David Foster, PhD, CEO

SAAM Institute, Inc.

---

From: "David S. Farrier"

Date: Thu, 04 Apr 2002 10:07:30 -0700

To: david.aaa.boomer.org

Subject: Re: PharmPK Formula for steady-state 2 compartment model

Rob,

Although our Excel-based PK Solutions pharmacokinetics analysis

program is designed primarily for easy computation of

noncompartmental pharmacokinetics, it does include the 2-comp

microconstants you mentioned above and will simulate and graph a

repeated dose regimen based on single dose data.

You are invited to download a list of equations and a demo to see if

this proves useful to your needs at www.SummitPK.com

Regards

David

David S. Farrier, Ph.D.

Summit Research Services

68911 Open Field Dr. Email: DFarrier.at.SummitPK.com

Montrose, CO 81401 Web: http://www.SummitPK.com

---

From: Spiresgate.at.aol.com

Date: Thu, 4 Apr 2002 12:18:17 EST

To: david.at.boomer.org

Subject: PharmPK Formula for steady-state 2 compartment model

Dear Rob

The question is a bit confusing; presumably at steady-state the concentration

is constant.

However assuming you mean how do you model the concentration-time profile for

multiple doses then this can be done relatively simply using a spreadsheet.

The way to do it is best demonstrated with a spreadsheet example but David

will not allow attachments; I can send an example directly to you if you

wish.

[Files like these can be placed on web or ftp sites for download and

a link included in the message - db]

The key to the multiple dose simulation is to add the dose at preset time

intervals to the dosing compartment. I usually do this by adding an 'if'

statement to the formula for the dosing compartment, the simplest example

being:

if(b2=60,100,0)

where b is the column containing the time value, and the dose is 100.

Hope this makes some sense,

Joe Chamberlain

[After a single IV bolus C = A*exp(-a*t) + B*exp(-b*t). After a

regimen of the same bolus dose given at a regular intervals, T, the

equation becomes C = A*[(1-exp(-n*a*T))/(1-exp(-a*T))]*exp(-a*t) +

B*[(1-exp(-n*b*T))/(1-exp(-b*T))]*exp(-b*t)

where n is the number of doses and t is the time since the last dose.

See http://www.boomer.org/c/p1/Ch14/Ch1407.html for the one

compartment example

If the doses or intervals are not the same then you need to calculate

for each dose separately and add them together

(http://www.boomer.org/c/p1/Ch15/Ch1504.html).- db]

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 "Formula for steady-state 2 compartment model" as the subject

PharmPK Discussion List Archive Index page

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