Physicochemical properties of enteric films prepared from aqueous dispersions and organic solutions.

Cast films composed of mixtures of Eudragit S100:L100 (1:1) and plasticized with triethyl citrate (TEC) were prepared from aqueous dispersions and organic solutions, and the physicochemical properties and the weight loss of cast films during dissolution testing were examined. The tensile strength of the organic cast films was significantly higher and the percent elongation was lower than that of the aqueous cast films. The weight loss of the organic films was also lower than that of the aqueous films. Furthermore, leaching of the TEC from the aqueous films was rapid and the TEC was found to diffuse from the films within one hour at pH 6.0, the pH at which the Eudragit S100:L100 (1:1) films were insoluble. In contrast to the aqueous films, minimal levels of the TEC diffused from the organic cast films, and the disintegration of acrylic polymers occurred simultaneously with the release of TEC from the film during dissolution testing at pH 7.0. For Eudragit L100-55, which could form films at lower TEC levels than Eudragit S100:L100, both the organic and aqueous films showed the same weight loss after four hours in pH 5.0 media. These results demonstrated that for Eudragit S100:L100 cast films, the high levels of TEC needed for film formation from aqueous dispersions resulted in rapid dissolution and disintegration at pH 6.0 and above. While aqueous dispersions are preferred for the coating of solid substrates, for Eudragit S100:L100 film coatings, a change from organic solutions to aqueous dispersions in the coating process will impact film properties and product performance.