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 of dressing performance are adhesive interactions with either moist mucosal tissue or skin and the wear time. Both the strength and the duration of adhesion are influenced by the hydration of the patches and the consequent modification of their physical structure. The hydration process is also linked to the build up of an osmotic pressure inside the hydrocolloid phase which, under suitable conditions, leads to the development of a measurable swelling force. The swelling force development 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 hydrocolloid dressings. Water uptake measurements were performed with a modified Enslin apparatus; it allows capillary water penetration from the adhesive surface of the patch, thus simulating in vivo conditions. Swelling force was measured by means of an apparatus previously described for measuring disintegrating force in pharmaceutical tablets. The apparatus was opportunely modified to carry out measurements on very thin samples. A correlation was found between the amount of water uptaken and the swelling force developed, which indicates that the two measurements provide complementary information on the patch performance.