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To assess bioequivalence for a drug with a half-life of 30 days, we have collected blood samples
within a 28-day dosing (infusion) interval at steady state.
We have stipulated that only two sampling occasions can be missed in each subject and not be
consecutive; also, the pre-dose, end of infusion and 28-day sample must be taken.
Pre-dose samples are also taken during the study to assess attainment of steady state.
One subject is not available for the 28-day sample during one period (can only be taken on Day 33);
is it reasonable to estimate the 28-day concentration by extrapolation?
Or should we take the pre-dose value as equivalent to the 28-day value?
As far as I can see, the FDA bioequivalence guidelines do not address sampling at steady state.
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Would it be extrapolation. You would have the preceding level and the later level for that patient.
You will a have model using the other subjects pre post and 28 day and you can work out how
predictable the 28 day levels are using the pre and post to calculate, then apply this to the
subject with the missing data.
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Hi Ed,
Your suggestion to assess the predictability (of extrapolation) with other subjects is a nice
approach.
Thanks,
Charlie
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It is interpolation so long as you have the preceding and following measure
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