Solubility parameter based drug delivery system and method for altering drug saturation concentration.

The method of adjusting the saturation concentration of a drug in a transdermal composition for application to the dermis, which comprises mixing polymers having differing solubility parameters, so as to modulate the delivery of the drug. This results in the ability to achieve a predetermined permeation rate of the drug into and through the dermis. In one embodiment, a dermal composition of the present invention comprises a drug, an acrylate polymer, and a polysiloxane. The dermal compositions can be produced by a variety of methods known in the preparation of drug-containing adhesive preparations, including the mixing of the polymers, drug, and additional ingredients in solution, followed by removal of the processing solvents. The method and composition of this invention permit selectable loading of the drug into the dermal formulation and adjustment of the delivery rate of the drug from the composition through the dermis, while maintaining acceptable shear, tack, and peel adhesive properties.