Bioequivalence and Bioavailability Forum

Dear Helmut,

❝ But it’s simple (use at least triplicates):

❝ • spike whole blood at 37 ℃^* as you would do with plasma, homogenize

❝ • centrifuge one set immediately

❝ • keep the others at ambient temperature (let them cool down) and centrifuge sets after e.g., 5, 10, 15, 20, 30, 45 minutes

That's indeed the easiest solution, but not always applicable. If your molecule has a high distribution or binding to the red blood cells, it may take some time after spiking to reach an equilibrium. In that case you will see a decrease of the plasma concentration over time, which will not be due to instability but to this partitioning or binding. That's one of the reasons why the EBF recommended to use a "qualified" whole blood method. However this recommendation is discussed. In the same issue of Bioanalysis journal the GCC recommended your approach, and to only go for a direct evaluation in whole blood if a partitioning or binding problem is expected or suspected.

Regards
Ohlbe