THE MINIWID-COATER .2. COMPARISON OF ACID RESISTANCE OF ENTERIC-COATED BISACODYL PELLETS COATED WITH DIFFERENT POLYMERS

Neutral pellets were loaded with bisacodyl and enteric-coated with hydroxypropyl methylcellulose acetate succinate (HPMCAS), carboxymethyl ethylcellulose (CMEC), cellulose acetate trimellitate (CAT), and poly(ethylacrylate, methacrylic acid) (Eudragit L 30 D) in a miniature fluid-bed pan coater called MiniWiD. Gastric juice resistance was tested by dissolution using USP Apparatus 2 (paddle) in 0.1 N hydrochloric acid under sink conditions over 6 hours. As a measure of enteric coating quality the USP specifications were used meaning that no more than 10 % of the drug should be released within 2 hours. Organic-solvent based films of HPMCAS, CMEC and CAT at a coating level of 18 to 25 % provided gastroresistance for more than 6 hours. Aqueous suspensions of HPMCAS and CMEC as well as the ammonium salt aqueous solutions of CAT produced films with a short gastroresistance of below 0.0 hours. By doubling the coating level of water-based HPMCAS films the protection was prolonged to 3.4 h. Enteric coatings were obtained from all aqueous latex dispersions of Eudragit L 30 D at a coating level of 24 %. The alteration of coating temperature between 25 and 45-degrees-C had no significant effect on the release rates, whereas the variation of type and amount of plasticizer led to a different release rate after 2 hours. Best protection was obtained using films plasticized with 20 % of dibutyl phthalate (DBP) allowing a release of only 4 % of the drug in 6 hours although the application temperature was 15-degrees-C below the minimum film-forming temperature (MFT). All coatings dissolved in artificial intestinal fluid within 15 minutes.