Pluronic block copolymers are found to be an efficient drug delivery system with multiple effects. The incorporation of drugs into the core of the micelles formed by Pluronic results in increased solubility, metabolic stability and circulation time for the drug. The interactions of the Pluronic unimers with multidrug-resistant cancer cells result in sensitization of these cells with respect to various anticancer agents. Furthermore, the single molecular chains of copolymer, unimers, inhibit drug efflux transporters in both the blood-brain barrier and in the small intestine, which provides for the enhanced transport of select drugs to the brain and increases oral bioavailability. These and other applications of Pluronic block copolymers in various drug delivery and gene delivery systems are considered.