Abstract

An improved iontophoresis device for topical administration of ionic drugs or chemicals through epidermal tissue for anesthetizing or sterilizing local tissue or for applying various medicaments without mechanical penetration. An ionic form of drug is conducted through the epidermal tissue by means of direct current generated from a battery powered current source. Pulse-width modulated DC current is regulated by feedback circuitry which varies the pulse duration and adjusts and stabilizes the average current at a desired level. A high voltage capability together with feedback control enables maintenance of a constant current through the highly resistive epidermal tissue. To prevent excessive voltage buildup and the accompanying dangers of shock and burns, a comparator circuit monitors current flow and voltage across the electrodes and automatically triggers an SCR shutdown circuit when impedance readings are outside predetermined limits. The ionic drug is suspended in a conductive gel mixture which acts as the conducting medium in direct communication with the patient's skin. This gel is carried in a receptacle mounted on an electrode pad which uses a conducting foil surface to make electrical contact with the gel.