Compositions and methods for controlling transdermal drug delivery, particularly of amine-functional and basic drugs, comprising a blend of a first silicone-based polymer having a reduced silanol concentration and a second silicone-based polymer have a substantial or high silanol concentration. The blend of such silicone-based polymers, particularly pressure-sensitive silicone adhesives, provides sufficient drug solubility and reduced initial drug delivery onset to permit a prolonged delivery duration at a substantially zero-order rate of delivery.