Device for administering drug transdermally which provides an initial pulse of drug

A device for administering a drug through intact skin that provides an initial pulse in the flux of the drug through the skin followed by a substantially lower flux of drug through the skin comprising in combination:

• (a) a reservoir comprising the drug and a volatile permeation enhancer having a vapor pressure greater than about 10 mm Hg at 25 .degree. C.;
• (b) a backing layer overlying the reservoir that is permeable to the volatile permeation enhancer such as to permit essentially complete evaporation of the enhancer to occur within 0.1 to 10 hours from the time at which the said permeable backing layer is exposed to the atmosphere, and
• (c) means for maintaining the device on the skin in drug and permeation enhancer transferring relationship thereto, whereby when the device is placed on the skin, the volatile permeation enhancer is depleted from the reservoir by evaporation through the backing layer with the magnitude and duration of the pulse being dependent among other things upon the permeability of the backing layer to the enhancer.