ABCB1 is a gene that provides instructions for making a protein known as P-glycoprotein. This protein plays a crucial role in transporting various substances across cell membranes, particularly in the liver, intestines, and blood-brain barrier. By doing so, it helps regulate the absorption and elimination of drugs and toxins from the body. Mutations or variations in the ABCB1 gene can affect how individuals respond to certain medications, influencing their effectiveness and potential side effects. Understanding ABCB1 is important in the field of pharmacogenomics, which studies how genes impact drug response and can guide personalized medicine approaches.