Efflux pump inhibitors: a strategy to combat P-glycoprotein and the NorA multidrug resistance pump.

Multidrug resistance (MDR) is the cause of an ever-increasing number of problems in the treatment of cancers and bacterial infections. The active efflux of drugs contributes significantly to this phenomenon. This minireview summarizes recent advances in combating MDR, with particular emphasis on natural and synthetic efflux pump inhibitors of P-glycoprotein in resistant tumor cells and of the NorA MDR pump in Staphylococcus aureus.