Cyprotex is a specialist provider of ADME and PK services and provide a range of in vitro protein binding assays.
Plasma protein binding and whole blood binding
Plasma protein binding and red blood cell binding plays an important role in the distribution and pharmacokinetics (PK) of a potential drug. In general, only unbound drug is available for passive diffusion to extravascular or tissue sites where therapeutic effects occur and therefore plasma protein binding is an important determinant of drug efficacy.
Parameters determined using plasma data (e.g., pharmacokinetic parameters) may be misleading if concentrations of drug differ between plasma and red blood cells as a consequence of differential binding to a specific component in the blood. The blood to plasma ratio determines the concentration of the drug in whole blood compared to plasma and provides an indication of drug binding to erythrocytes.
Drug that is sequestered in microsomes in vitro is presumed to be unavailable for direct interaction with metabolizing enzymes, just as drug that is bound to plasma proteins and tissue macromolecules in vivo is presumed to be unable to be directly acted on by drug metabolizing enzymes. Microsomal binding is an important factor in the prediction of in vivo pharmacokinetics from in vitro drug metabolism data and the prediction of drug-drug interactions.