Formulation of sildenafil citrate loaded nasal microsphers: An in vitro, ex vivo characterization

The aim of the present study was to prepare gellan gum microspheres of Sildenafil citrate, for intranasal delivery to avoid the first pass metabolism. The microspheres were prepared using spray drying method. The microspheres were evaluated for characteristics like particle size, incorporation efficiency, swelling ability, zeta potential, in-vitro mucoadhesion, ex-vivo mucoadhesion, thermal analysis, XRD study and in-vitro drug release. Treatment of in-vitro data to different kinetic equations indicated diffusion controlled drug delivery from gellan gum microspheres. The results of DSC and XRD studies revealed the molecular amorphous dispersion of Sildenafil citrate into the gellan gum microspheres. Microspheres so prepared were discrete, bulky, free flowing and showed an average encapsulation efficiency ranging from 95-98%. The formulation exhibited a good mucoadhesive strength which was determined in in vitro conditions through falling film technique and was compared with ex vivo studies. The microspheres so prepared also exhibited a good swelling index which confirmed the strong mucoadhesive property of the formulation. Keywords: Gellan gum, Microsperes, Spray drying, Sildinafil citrate, Nasal delivery.