The present invention is directed to polymeric matrices for the controlled
release of a hydrophilic bioactive agent. Generally, the elution control
matrix includes a polymeric matrix having a first polymer and a plurality
of microparticles that include the hydrophilic bioactive agent. In one
embodiment, the matrix includes a polymer comprising hydrophilic and
hydrophobic portions. In another embodiment, the microparticles include a
crosslinked hydrophilic polymer.