An electrotransport agent delivery device (10) for delivering a therapeutic agent through intact skin, and a method of operating same, is provided. The device applies a pulsing electrotransport current wherein the length of the applied current pulses is at least 5 msec and preferably at least 10 msec. Most preferably, the current pulses have a magnitude above a critical level (I.sub.c) at which the skin is transformed into a higher electrotransport delivery efficiency (E) state.