Various systems and methods provide iontophoretic delivery of anesthesia at a patient's tympanic membrane. Some implementations provide channel switching enabling a single current sink to pull current through two electrodes in an alternating fashion based on clock pulses. The iontophoretic delivery of anesthesia may be driven by an AC modulated current. Some imple-mentations provide for continuous flow of fresh iontophoresis fluid to the ear canal during iontophoresis. The fluid flows from a source reservoir into the cavity between the tympanic membrane and a plug, and then drains out of the cavity to a reservoir. An ion-tophoresis system may also detect capacitance between an anode electrode and an auxiliary electrode in a patient's ear canal, watch-ing for reduced capacitance to indicate presence of a bubble in the iontophoresis fluid.
