Bioequivalence and Bioavailability Forum

❝ Can you clarify what is the use of taking more than one predose samples and in which conditions/drugs it will be considered.

1. In single dose studies you will take predose samples in every treatment period (TP) as a demonstration of proper design (TP=1: suitability of bioanalytical method = lacking interferences, TP≥2: wash-out long enough = lacking carry-over).
   
2. In multiple dose studies you will take more predose samples in every TP (at least three) in order to demonstrate steady state conditions. If total blood loss allows, all predose samples should be drawn as a compliancy control.
   
3. In studies of endogenous compounds (stable baseline = no/low circadian variation) you may take more than one predose sample in every period - either shortly before administration (e.g. -1, -0.5, 0 h) or throughout the previous day in order to minimize variation (taking the mean for correction of measured concentrations).