The present invention relates to an vitro device for the removal of ionized substances from a membrane sample without mechanical penetration, which device comprises:(a) a positive electrode;(b) a negative electrode, and(c) electrical insulation between subpart (a) and (b), wherein the positive electrode, and the negative electrode, and electrical insulation are positioned on the same side of the membrane sample.The present invention also relates to a device for the removal of or delivery of ionized substances to a mammal through intact skin or mucosal membrane without mechanical penetration, which device comprises: (a) a positive electrode, (b) a negative electrode, and (c) an electrically insulating material between subpart (a) and (b), wherein the positive electrode, negative electrode and insulating material are physically positioned so that each present a common surface of the device for contact with the same surface of the skin or mucosal membrane of the mammal.The present invention also relates to the use of iontophoresis to determine the level of a charged molecule in a living mammal, and with the use of a feedback mechanism, administer appropriate levels of therapeutic substances.