Effect of Poly Ethylene Glycol Blending on Triptorelin Release from PLA Microspheres

Triptorelin is a superagonist decapeptide analogue of GnRH, which has higher binding affinity for the GnRH receptors, a prolonged half-life and therefore a greater potency, 100 times more than GnRH. Different triptorelin controlled release formulations are available in the market. In this study, triptorelin microspheres were successfully prepared using poly lactide (PLA) and poly ethylene glycol (PEG) blends with different ratios and different techniques. The effect of various factors on surface morphology, drug loading, particle size, size distribution, in vitro release and thermal analysis were evaluated. The particle size diameter was ranged from 62 to 145 μm. The impact of oil phase volume on the particle size was the greatest. The optimum drug loading (6.8 or 7.9%) was achieved when the concentration of PEG was 10% or the pH of the system was at isoelectric pH of the external continuous phase, respectively. All the formulations showed continuous drug release with a small burst release. It can be concluded that both diffusion and erosion mechanism contributed in drug release.