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The following message was posted to: PharmPK
I have only started using Winnonlin for more complicated datasets and
have a question that is likely elementary, but I can't seem to get
anyone that I have asked to provide an answer......
The Question:
When you have patients receiving twice daily dosing of a drug (at steady
state), but the dose in the Am is different than the dose in the PM, how
is this explained to Winnonlin. The dosing tab has a blank for one dose
only? Response(s) are very appreciated. Thanks.
Melanie S. Joy, Pharm.D., FCCP
Associate Professor
UNC School of Medicine
Division of Nephrology and Hypertension
UNC Kidney Center
CB #7155, 7005 Burnett Womack Building
Chapel Hill, NC 27599-7155
919-966-2561 ext 259 (phone)
919-966-4251 (fax)
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The following message was posted to: PharmPK
Melanie,
Non-compartmental analysis in WinNonlin will accommodate only one
dose and
dosing time for steady-state and single-dose calculations. Multiple
dosing
is allowed for compartmental modeling. There are ways to get around the
limitation with the NCA engine. If you have PK samples after both doses,
then you can use the 24hr profile and the total daily dose. When PK
samples
are only available after only one dose, then you use the
superposition tool
to impute the missing concentration data.
Cheers... Brian
Brian M. Sadler, PhD
Strategic PK Consulting, LLC
1209 Seabrook Avenue
Cary, NC 27511
USA
bsadler1.at.nc.rr.com
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Hi Melanie,
When you change the number of doses to be more than 1, you are
automatically given the option to enter different doses along with
the time for each dose.
Hope that helps!!
Ahmed
--
Ahmed Abdel-Fattah Othman
Ph.D. Candidate
Pharmacokinetics and Biopharmaceutics lab
School of Pharmacy
University of Maryland at Baltimore
20 Penn Street,HSF-2
Baltimore, MD 21201
E-Mail:- aothm001.aaa.umaryland.edu
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The following message was posted to: PharmPK
Melanie,
Both Brian and Ahmed were correct; to be able to use multiple doses
in your analyses you will have to select Compartmental modelling.
If you are using any of the NCA models then any dose dependent output
parameters will only be 'appropriate' if you are analysing data from
the last dose in the profile > hence the field in the WinNonlin model
is called "Time of Last Dose" e.g. if you had twice daily dosing for
7 days then the Steady state assessment would be on a Tao of 12
hours, the data to be analysed would be Days 7, 12-24hrs.
One final note I would also suggest caution when using the
superposition tool as you are assuming linear Kinetics, which you may
find is not the case when you compare predicted versus actual
accumulation. There is a discussion here that you may find useful;
http://www.boomer.org/pkin/PK01/PK2001159.html.
Please feel free to pass similar technical questions relating to our
software to support.aaa.pharsight.com, you may also wish to consider one
of our hands on courses; http://www.pharsight.com/training/
course_display_new.php?details_id=46
Best regards,
Simon.
--
Simon Davis
Pharsight
Facsimile : +1 801 991 7145
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The following message was posted to: PharmPK
Dear Ahmed,
Your point is true but more appropriate method is to have dosing data
in another worksheet and load this sheet through 'Dosing Data
Variable' tab in 'Model' option. This way you can address many
scientific issues e.g. different weights, different doses, different
time of dosing, multiple dosing etc. While developing models or rerun
model many times, you need not to feed doses again and again. Just
load the sheet and WinNonlin will incorporate the information
internally. This way you can preserve the information more
appropriately in your database. It's better to insert two worksheets
in one workbook, one for concentration time data and another for
dosing information for convenience.
Regards,
Sukhbir Singh
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Definitely Sukhbir, depending on how big the data set is.
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