Used to measure P-glycoprotein (PGP) activity in human biological samples such as serum, plasma, or cell lysates. It is commonly applied in pharmacokinetic and drug resistance studies, especially in cancer research where PGP overexpression is linked to reduced drug efficacy. The kit helps assess how drugs interact with PGP, aiding in the development of new therapeutics that can bypass multidrug resistance. It is also used in clinical labs to monitor PGP function in patients undergoing treatment with substrates of PGP, such as certain chemotherapeutics, immunosuppressants, or antivirals.