roody
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2005-08-30 19:06

Posting: # 25
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 ethnic variations [Power / Sample Size]

Does the variability remains the same in different population (US or Europe/Japan Vs. India) while calculating the sample size for pivotal BE studies? How to overcome the ethnic variations (sample size calculation) in pharmacokinetic studies?
Helmut
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2005-09-02 13:41

@ roody
Posting: # 26
Views: 11,698
 

 ethnic variations

Dear roody!

» Does the variability remains the same in different population (US or Europe/Japan Vs. India) while calculating the sample size for pivotal BE studies?

I think this a complex issue, even assuming you are not talking about bridging studies (viz. comparisons between different ICH regions)!

If you are talking about cross-over studies, differences between populations – mainly caused by polymorphism – should not be a major problem: e.g., slow metabolizers show higher levels both after test and reference, i.e., the treatment-ratio should be the same as in fast metabolizers.

If you are talking about parallel designs, e.g., for drugs with a long half life, or studies in patients – sample sizes suitable in one population may be entirely insufficient in an other, since the total variability (intra- plus intersubject) may be different.

» How to overcome the ethnic variations (sample size calculation) in pharmacokinetic studies?

It should not be a big problem in cross-over studies, although it may be wise to allow for some ‘safety margin’ in sample size extrapolating from one population to an other.
For parallel designs you should be (very!) weary. For example you can run into analytical problems, if your target population consists mainly of extensive metabolizers…

Cheers,
Helmut Schütz
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