An adhesive matrix and adhesive formulation are described. The adhesive matrix is comprised of a hydrophilic domain and a hydrophobic domain, and a therapeutically active agent contained in the matrix in a supersaturated, stable, condition. The hydrophilic domain and the hydrophobic domain are co-soluble in a solvent system, to provide a homogeneous blend in which the active agent is solubilized. The proportion of the hydrophilic domain and hydrophobic domain is selected to optimize, or maximize, solubility of active agent in the matrix.