COMPARATIVE-EVALUATION OF HYDROCOLLOID DRESSINGS BY MEANS OF WATER-UPTAKE AND SWELLING FORCE MEASUREMENTS .1.

Composite hydrocolloid dressings are used in medical practice for both skin and mucosal applications. The most important features in terms o f dressing performance are adhesive interactions with either moist muc osal tissue or skin and the wear time. Both the strength and the durat ion of adhesion are influenced by the hydration of the patches and the consequent modification of their physical structure. The hydration pr ocess is also linked to the build up of an osmotic pressure inside the hydrocolloid phase which, under suitable conditions, leads to the dev elopment of a measurable swelling force. The swelling force developmen t provides information on the modification of dressing structure and, in particular, how the patches disintegrate. Water uptake and swelling force measurements are used to characterise and compare different hyd rocolloid dressings. Water uptake measurements were performed with a m odified Enslin apparatus; it allows capillary water penetration from t he adhesive surface of the patch, thus simulating in vivo conditions. Swelling force was measured by means of an apparatus previously descri bed for measuring disintegrating force in pharmaceutical tablets. The apparatus was opportunely modified to carry out measurements on very t hin samples. A correlation was found between the amount of water uptak en and the swelling force developed, which indicates that the two meas urements provide complementary information on the patch performance.