The blood to plasma ratio (often referred to as Kb/p) is the ratio of the concentration of drug in whole blood (i.e. contains both red blood cells and plasma) to the concentration of drug in plasma, namely CB/CP.

The blood/plasma ratio of the test compound helps to understand whether the compound enters and binds to the protein in blood cells. If the whole blood/plasma distribution ratio is greater than 1, it means that the compound enters the blood cells and the PK parameters calculated with the plasma concentration will not reflect the PK properties of the compound well.

Blood to Plasma Ratio Assay Protocol

SpeciesRat, mouse, dog, monkey, human
Test concentration0.5 µM (other concentrations can be used)
Positive ControlMethazolamide (human)
Chlorthalidone (rat and mouse)
Chloroquine (dog)
Compound required100 µL 10mM DMSO solution or 2 mg
Analysis methodLC-MS/MS
Data DeliveryMean±SEM of blood to plasma ratio

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