This invention relates to an improved transdermal drug delivery device for the controlled transdermal delivery of amino-functional drugs. The improvement resides in providing the device with a silicone pressure-sensitive adhesive layer which has been chemically treated to reduce the silicon-bonded hydroxyl content of the pressure-sensitive adhesive composition to render the adhesive layer resistant to loss of tack and preserve the instant adherence of the device to the skin of a wearer during storage and while the device is being worn. Preferably, the composition used comprises a silicon-bonded hydroxyl radical containing resinous copolymer of R.sub.3 SiO.sub.1/2 units and SiO.sub.4/2 units and a polydiorganosiloxane which have been chemically treated with R.sub.3 SiO.sub.1/2 units where R is preferably a hydrocarbon radical such as a methyl group to reduce the silicon-bonded hydroxyl content of the adhesive and thereby its sensitivity to amino-functional drugs.