Drug–drug interactions affected by the transporter protein, P-glycoprotein (ABCB1, MDR1)

The simultaneous use of several drugs (polypharmacy) for the treatment of cancer, HIV, and other diseases and for multiple ailments of the elderly is a common practice in modern medicine. Co-administration of drugs may result in unwanted side effects. One reason for these side effects can be the altered function of transport proteins, especially of P-glycoprotein (Pgp), due to its simultaneous interaction with several drugs. We describe here some of the observed, unexpected side effects of polypharmacy in the clinic. We also describe intentional modulation of the function of Pgp that is introduced when facilitation of absorption of a drug through the intestines is needed and in cancer chemotherapy. In addition, we mention some methods of testing and ways by which doctors and patients can be alerted to potential side effects.