THE PHYSICAL AND CHEMICAL-STABILITY OF SUSPENSIONS OF SUSTAINED-RELEASE DICLOFENAC MICROSPHERES

The major challenge in liquid sustained-release oral suspensions is to minimize drug diffusion into the suspending medium and to retain the original properties of the microparticles during storage. Diclofenac w ax microspheres prepared by the hydrophobic congealable disperse phase method were formulated as a sustained release suspension and stored a t three different temperatures (25, 37 and 45 degrees C) for 3 months, to evaluate the physical and chemical stability of the suspended micr ospheres. Suspensions of microspheres stored at ambient temperatures w ere both physically and chemically stable, but at higher temperatures, up to 45 degrees C, there was a decrease in drug release due to scali ng and melting on the microsphere surface as observed by scanning elec tron microscopy. However, on prolonged storage, up to 90 days, especia lly at 45 degrees C, temperature became a dominant factor causing an i ncrease in drug release. The suspension of diclofenac microspheres was chemically stable for 3 months, while the plain drug suspension exhib ited slight degradation.