Development of 5-iodo-2 '-deoxyuridine milling process to reduce initial burst release from PLGA microparticles

The aim of this study was to prepare 5-iodo-2'-deoxyuridine (IdUrd) loaded poly(d,l-lactide-co-glycolide) (PLGA) microspheres with a reduced initial b urst in the in vitro release profile, by modifying the drug grinding condit ions. IdUrd particle size reduction has been performed using spray-drying o r ball milling. Spray-drying significantly reduced drug particle size with a change of the initial crystalline form to an amorphous one and led to a h igh initial burst. Conversely, ball milling did not affect the initial IdUr d crystallinity. Therefore, the grinding process was optimized to emphasize the initial burst reduction. A first step allowed us to set qualitative pa rameters such as ball number (7) and cooling with liquid nitrogen to obtain a mean size reduction and a narrow distribution. In a second step, three p arameters including milling speed, drug amount and time were studied by a r esponse surface analysis. The interrelationship between drug amount and mil ling speed was the most significant factor. To reduce particle size it shou ld be necessary to use a moderate speed associated with a sufficient drug a mount (400-500 mg), IdUrd release from microparticles prepared bg the o/w e mulsion/extraction solvent evaporation process with the lowest crystalline particle size (15.3 mu m) was studied. Burst effect could be reduced signif icantly. Concerning the first phase of drug release, the burst was 8.7% for 15.3 mu m compared to 19% for 19.5 mu m milled drug particles. (C) 1999 El sevier Science B.V. All rights reserved.