Formulation and Evaluation of Controlled Release Microspheres of Zidovudine

The aim of this study was to formulate and evaluate microencapsulated controlled release preparations of zidovudine, using Copolymers Eudragit S 100 and RL 100 (acrylic and methacrylic acid esters) and Ethyl cellulose as the retardant material. Microspheres were prepared by solvent evaporation method using an acetone/liquid paraffin system. Magnesium stearate was used as the droplet stabilizer and n-hexane was added to harden the microspheres. The prepared microspheres were characterized for their micromeritic properties, drug loading, as well by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The in vitro release studies were performed in pH 7.4, phosphate buffer. The prepared microspheres were white, free flowing and spherical in shape. The drugloaded microspheres show 81-93% of entrapment and release was extended more than 10hrs. Stability studies revealed that polymers used were stable and compatible with the drug and there is no significant effect on physical characteristics, drug content and dissolution profile of the microspheres. Scanning electron microscopy study revealed that the microspheres were spherical with rough surface. The best-fit release kinetics was achieved with Higuchi's plot followed by First order and Zero order. The release of Zidovudine was influenced by the drug to polymer ratio, particle size&was found to be diffusion controlled.