A system for delivering a substance into a body at a treatment site that includes an alternating current source and a plurality of electrodes. Circuitry is connected between the alternating current source and the electrodes for supplying current to the electrodes when the electrodes are in electrical contact with said body so that a uni-directional current flow for delivering the substance into the body is maintained at the treatment site and a bi-directional current flow is maintained throughout the body. At least one of the electrodes is divided into sub-electrodes to, for example, reduce hazards associated with current concentration. These and other systems and methods are adaptable for large treatment areas and/or use a convenient and low-cost arrangement of electronics.