Development and Evaluation of Stavudine Loaded Injectable Polymeric Particulate Systems

Abstract

Present research investigates the formulation of stavudine loaded biodegradable microspheres from different grades of Poly (D, L Lactide-co-glycolide) as a depot system for parenteral delivery. Prolonged release of stavudine facilitates reduction in symptoms of HIV infection and delay AIDS progression by reducing viral load to undetectable levels. Microspheres were prepared from PLGA 85:15 and PLGA 50:50 (RESOMER(®) 505H) by solvent evaporation technique with different drug/polymer ratios (1:4, 1:10, 1:20, 1:50, 1:100) and a polymer solution/vehicle ratio of 1:2. The effects of various formulation variables like polymer type and concentration, surfactant concentration and drug to polymer ratio on the characteristics of microspheres were evaluated. All thirteen formulations of microspheres were evaluated for yield, entrapment efficiency, particle size and In vitro release studies. Microspheres were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), residual solvent analysis and confocal laser scanning microscopy (CLSM). Microspheres showed excellent surface topography with uniform distribution and structural integrity of the drug. Resulting microspheres showed the maximum entrapment efficiency of 68.0 ± 1.62% and mean particle diameter below 100µ. Drug release kinetics data were obtained from various kinetic models and best explained by "Higuchi Kinetic" i.e. drug release was largely governed by diffusion through water-filled pores in the matrix. Korsmeyer-Peppas equation depicted that drug release mechanism is anomalous transport, i.e. diffusion as well as polymer relaxation. Drug release from microspheres exhibited the characteristic release pattern of a monolithic matrix system with a maximum of 80-90% drug release in 6-8 weeks demonstrating the feasibility of prolonged delivery of stavudine using biodegradable microspheres for parenteral depot system.