In vitro release characteristics and long term stability of poly(ethylene oxide) hydrogel vaginal pessaries containing prostaglandin E2

Abstract The clinical potential of prostaglandin E 2 (PGE 2 ) and PGE analogues in labour and abortion has not been fully realised because the products available hitherto lack long-term storage stability and current formulations do not provide the prolonged slow release which is required for this usage. These properties are achieved, however, by incorporating PGE 2 in a water swellable, polymer vaginal pessary (hydrogel) which is currently in clinical use. The formation of the device, comprising poly(ethylene oxide) cross-linked polymers, from formulations of moderate molecular weight polyethylene glycol, 1,2,6-hexane triol and pure dicyclohexylmethane-4,4'-diisocyanate and the incorporation of prostaglandins in the matrix is described. The prolonged release characteristics of the pessary have been demonstrated in vitro providing fairly constant release for the first fifty percent of the PGE 2 content dispersed in the matrix. The half life time can be controlled by the pessary thickness. Radioimmunoassay of the PGE 2 content indicated that when incorporated in the polymer pessary PGE 2 was evenly distributed and possessed long-term stability .