Usually I find that for a Phase 1 study e.g. a bioequivalence type study that the blood sampling times actually obtained in the clinical study are nearly always EXACTLY the same as the nominal times in the clinical protocol. The clinics are very efficient. I have been able to use the nominal times for the pharmacokinetic data analysis. I specify limits for the time of blood samples in the clinical protocol e.g. for a modified release (slow) formulation plus or minus 15 minutes deviation from nominal and for samples up to 24 hours and thereafter plus or minus 30 minutes is allowed. If the time of the blood sample is outside of these limits for nominal then I would use the actual time of that one sample instead of the nominal time.
If you consider the pipette used to aliquot a blood sample is accurate to plus or minus 2% and think of the other error sources then I feel time differences inside the stipulated time windows in AUC calculation as stipulated are not significant.
The other option is to always use actual times, but this creates a problem since the charts and tabulations in a report use the nominal times. So there is a difference and it serves to confuse.
Any thoughts on this topic?