The present invention relates to medical devices that are inserted or implanted into patients and that have antimicrobial coatings that release free radicals into the vicinity of the device. These devices may have coatings that alter their rate of flow release or elution release of an antibacterial agent from a coating on the device upon external stimulation. The coating should therefore be responsive to external control such as by heating, external RF stimulus, sonic control, visible or ultraviolet light exposure and the like. By having control of the release rate, and in some structures without invasion of the patient by mechanical means in addition to the device itself, the release rate can be in response to need at the implant site. The class of compounds to be released are free radical generating or initiating compounds, or compounds that release free radicals upon immersion or stimulation, the free radicals acting as the antimicrobial agent.