In vivo and in vitro evaluations of water-absorption properties of various ointments.

The water-absorption properties of various vehicles were evaluated in rats whose stratum corneum had been stripped off over the application site. Polyethylene glycol (PEG) applied to the site effectively absorbed the exudate, but other applied ointments absorbed little exudate or water. By the PEG ointment, the exudate was absorbed continuously and extensively, and a linear relationship was obtained between the amount of water absorbed and the square root of time. To establish an acceptable alternative in vitro method for the design of a suitable ointment for treating skin ulcers with exudate, in vitro evaluations were performed by three methods: the Franz cell method, the cellulose membrane diffusion method and the spontaneous water uptake method. The membrane diffusion method, and the spontaneous water uptake method appeared to be acceptable alternatives to the in vivo method in evaluating the water absorption of ointments. It is a simple and useful method for preliminary formulation studies of ointments for the treatment of skin ulcers with exudate.