In today’s medical climate, the anesthesiologist must be prepared to function as a specialist in perioperative medicine. This includes (among many other tasks) a thorough knowledge of the drugs commonly given not just in the operating room (OR), but in the perioperative period, including routes of administration, dosing, and the specifics of drug elimination. Although discussions of pharmacokinetic drug handling most often focus on issues of metabolism and excretion, the emerging importance of the P-glycoprotein transporter highlights the relevance of absorption and distribution as well. The P-glycoprotein transporter is an ATP-dependent pump that extrudes various compounds (substrates) from protected intracellular domains. For instance, P-glycoprotein lines the lumen of the small intestine. When a P-glycoprotein substrate is absorbed across its concentration gradient into the cytosol of an enterocyte, this transporter acts to then extrude that drug out of the enterocyte and back into the gut lumen. Insofar as this process moves the drug against its concentration gradient, it requires ATP. P-glycoprotein also lines the blood-brain barrier, acting as one of the constituents that minimizes access of xenobiotic substances to the central nervous system. In a manner analogous to the small intestine, P-glycoprotein substrates diffuse from the vasculature into the cytosol of blood-brain barrier capillary endothelial cells, but the pump then acts to extrude them back into the vasculature. Significant P-glycoprotein substrates include carbamazepine, corticosteroids, cyclosporine, dexamethasone, digoxin, morphine, ondansetron, phenytoin, risperidone, tacrolimus, and tricyclic antidepressants. Dose-finding studies to determine effective doses of these and other P-glycoprotein substrates have already incorporated these effects.