Ultrasonically modulated polymeric devices for delivering compositions

A process for delivering a biologically active substance on demand comprising the steps of:

• combining a biologically active substance with a biocompatible polymeric composition as an admixture;
• forming said admixture into a shaped, solid polymeric matrix;
• implanting said solid polymeic matrix in-vivo at a preselected site such that said solid implanted matrix is in a liquid environment;
• and
• exposing said implanted solid polymeric matrix to ultrasonic energy for a predetermined time to effect cavitation of said solid polymeric matrix by rapid compression with subsequent expansion of liquid or solid surrounding said solid polymeric matrix thereby to control the rate of release of said biologically active substance from said matrix over a specific time period wherein the rate of release is changed during said time period.