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The following message was posted to: PharmPK
Hi all,
I have two questions regarding bioequivalence studies:
1) WinNonlin outputs Westlake confidence intervals. When would it be
appropriate to use these confidence intervals and would they be
accepted by the FDA?
2) What is the correct way to do a sample size calculations for a
three way cross over study. I have 3 drugs to compare with 3
sequences. I am using nQuery advisory and I get a per group sample
size for a two group design. Is it correct to just multiply this
number by three - the sample size I am getting seems too high. Does
anyone have any references that would help with this?
Thank you in advance.
Laura
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The following message was posted to: PharmPK
Dear laura,
Sample size calculation depends on coefficient of variation. If
coefficient
of variation is large, automatically sample size will come large.
You can calculate sample size using SAS software. In that you can get
sample
size N per group. So If study is three period, multiply N with three,
so you
can get sample size.
regards
Srinivasa Reddy.E
Research Analyst
Bioserve Clinical Research Pvt Ltd
Hyderabad.
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The following message was posted to: PharmPK
Dear Laura!
>1) WinNonlin outputs Westlake confidence intervals. When would it be
>appropriate to use these confidence intervals and would they be
>accepted by the FDA?
>
Westlake's symetrical confidence interval is of historical interest
only and not accepted in any country...
IMHO they should be removed form WinNonlin...
>2) What is the correct way to do a sample size calculations for a
>three way cross over study. I have 3 drugs to compare with 3
>sequences. I am using nQuery advisory and I get a per group sample
>size for a two group design. Is it correct to just multiply this
>number by three - the sample size I am getting seems too high. Does
>anyone have any references that would help with this?
>
3 sequences are not adequate anyway; to compare 3 treatments you
should apply a 6-sequence William's design.
For details (including sample size estimation) look at this post
http://forum.bebac.at/forum_entry.php?id=50 and the followings.
best regards,
Helmut
--
Helmut Schuetz
BEBAC
Consultancy Services for Bioequivalence and Bioavailability Studies
Neubaugasse 36/11
1070 Vienna/Austria
tel/fax +43 1 2311746
Web http://BEBAC.at
BE/BA Forum http://forum.bebac.at
http://www.goldmark.org/netrants/no-word/attach.html
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