Studies comparing Kollicoat MAE 30 D with commercial cellulose derivatives for enteric coating on caffeine cores

The products that are processed in aqueous form, such as Aqoat MF (suspension), Aquateric (pseudolatex), HP 55 (ammonia-based solution), and Kollicoat MAE 30 D (latex), were compared (in the form of spray dispersions, isolated films prepared from the dispersions, and caffeine-film-coated tablets with 5.5, 8.0, and 11.0 mg film/cm2) with one another and with ethanolic HP 55 S solution. The addition of pigments to all of the liquid preparations, with the exception of the ammoniacal solution of HP 55, led to a slight increase in pH. In each case, the viscosity of both solutions was well above that of the other formulations. The minimum film-forming temperature was decidedly reduced by the addition of pigment. Kollicoat MAE was the undissolved film-former that had the smallest particle size and particle size distribution. The next smallest were those of Aqoat MF. The latex and the suspension were the only products that were sensitive to shear and heat. The isolated films did not display any tack. The strongest films and the films most impermeable to water vapor were obtained from solutions, and this can be ascribed to the fine distribution of the film-former. None of the isolated films showed signs of dissolving at pH 4.5. At pH 5.5, only the HP 55 was dissolved. This was because HP 55 was processed in ammonia-based solution; as a result of which, films that were not very resistant to gastric juice were obtained. The other formulations did not dissolve until the pH reached 6.0. As the pH rose, the rate of dissolution increased for all of the films. The permeability to protons was similar to that of caffeine-film-coated tablets to gastric juice. The resistance increased in the following sequence: HP 55 (ammonia-based) < Aquateric < Aqoat MF < HP 55 S (organic) and Kollicoat MAE. As a result of the temperature treatment and the rate of spraying, the production time on a 5-kg scale was twice as long for 5.5 mg Aqoat MF/cm2 as it was for Kollicoat MAE. This amount of film sufficed for Kollicoat MAE and HP 55 S solution to achieve adequate resistance to gastric juice. Aqoat MF did not attain the same resistance until a thickness of 11 mg film/cm2 was reached. Film tablets with Aquateric and ammonia-based HP 55 solution absorbed more than 20% of gastric juice at this film thickness.