CONTROLLED DRUG DELIVERY SYSTEMS BASED UPON BIODEGRADABLE MICROPARTICLES WITH INCREASED SUSPENDABILITY

BIODEGRADABLE MICROPARTICLES ARE BEING STUDIED EXTENSIVELY TO DELIVER A WIDE VARIETY OF DRUGS IN A CONTROLLED MANNER. DESIRED RELEASE PROFILES CAN BE ACHIEVED BY JUDICIOUS CHOICE OF BIODEGRADABLE POLYMER, PARTICLE SIZE, AND DRUG LOADING. THESE RELEASE PROFILES MAY LAST FROM WEEKS TO YEARS, DEPENDING UPON THE MATERIALS AND PARAMETERS USED. ONE SIGNIFICANT OBSTACLE IS THE DIFFICULTY OF ADMINISTERING THESE MICROPARTICLES BY INJECTION BECAUSE OF THEIR TENDENCY TO SETTLE QUICKLY IN THE USUAL VEHICLES SUCH AS SALINE. THIS IS A SIGNIFICANT PROBLEM IN PRACTICE, NOT ONLY BECAUSE THE SETTLING MAKES IT DIFFICULT TO ADMINISTER THE ENTIRE INJECTION VOLUME OF MICROPARTICLES MAY HAVE A TENDENCY TO CLUMP IN THE NEEDLE OF THE SYRINGE, MAKING AN INJECTION IMPOSSIBLE. VISCOUS INJECTION MEDIA IS CURRENTLY THE PROCEDURE USED TO ATTEMPT TO INJECT BIODEGRADABLE MICROPARTICLES. A NOVEL, METHOD WITH WHICH BIODEGRADABLE MICROPARTICLES CONTAINING DRUGS CAN BE SURFACE TREATED SO THAT THEY CAN BE SUSPENDED IN AQUEOUS MEDIA OR LONG PERIODS OF TIME IS DESCRIBED. THE NOVEL TECHNIQUE IS BASED ON PROCESSES OF THE STAR-BURST TYPE.