The invention provides a local concentration management system (LCMS) for delivery of highly concentrated therapeutic agent formulations. The LCMS comprises a device comprising an elongate body defining a lumen between its proximal and distal ends, and a diffuser element, a dilutor element, or both. The diffuser element, which is selectively permeable to the agent, is operatively associated with the elongate body so that agent flows through the elongate body, and into and through the diffuser element to exit the system. The dilutor element can be operatively associated with the system to be in fluid communication with the elongate body lumen, a diffusion space defined by a diffuser element inner wall, or both. The dilutor element is selectively water permeable, but substantially impermeable to agent, to provide for dilution of the agent during transit through the system. The LCMS system is designed to disperse and/or dilute the drug delivery stream.