In vivo evaluation of the vaginal distribution and retention of a multi-particulate pellet formulation

Abstract

Non-disintegrating microcrystalline cellulose pellets (MCC) and disintegrating starch-based pellets were evaluated as new vaginal drug delivery forms and compared with a powder formulation. Pellets and powder were packed in a HPMC or hard gelatine capsule and vaginally administered to five series of five healthy volunteers. Distribution and retention of the multi-particulate formulation was monitored by colposcopy and swabbing. Capsule disintegration in the vagina was slow. MCC pellets clustered around the fornix 3h after administration, and after 24h only a few pellets were detected in the vaginal cavity. In contrast, starch-based pellets already started to disintegrate 6h after administration, resulting in a complete coverage of the vaginal mucosa after 24h in 8 out of 10 volunteers. The powder formulation had a better distribution after 6h, although after 24h almost no powder remained in the vagina. These results were confirmed by swabbing to determine the amount of riboflavin sodium phosphate (used as marker) distributed in the different vaginal regions.