Abstract
Water vapour transmission through free and applied film of four Eudragit resins namely, E100, L100 and RS100 to directly compressed thiamine hydrochloride tablets was investigated. The type of Eudragit film influenced both water vapour transmission and moisture absorption characteristics of the tablets compressed with either single or binary blend of vehicles. The moisture absorption rate constant Ka, for a given batch was found to be a function of vapour pressure, P, and film thickness, L. The relationship between Ka and either of these parameters is exponental and may be expressed as Ka = A exp (x/P) and Ka = K*a exp (-x*L). In general, film coating with Eudragit resins affected the physical characteristics of the tablets. The rate of drug release, K has an exponentially relationship as Ke Ko exp (-c/L).