Adjustable electrotransport drug delivery using a fixed output controller

The invention provides a method for adjusting, i.e., varying, the rate of delivery of a therapeutic agent through a body surface from an electrotransport assembly of the type which includes a predetermined, e.g., fixed, output electronic controller and a detachable therapeutic agent source. The method provides a plurality of therapeutic agent sources in which a single parameter or a series of parameters has been varied. The plurality of agent sources are supplied, one at a time, to the controller of the electrotransport assembly, so that together (i.e., source and controller) the agent delivery rate is varied.