Variation of composition of an enteric formulation based on Kollicoat MAE 30 D.

Using a formulation described previously with Kollicoat MAE 30 D as the film-forming agent, the effect of variations in plasticizer type and quantity and talc concentration on the preparation and processing of spray-coating suspensions and the properties of isolated films and film-coated caffeine tablets prepared using them was investigated. In the preparation and processing of spray-coating suspensions, the plasticizers polyethylene glycol (PEG) 400, PEG1500, and TEC (triethyl citrate) tended to coagulate at all concentrations investigated, while Cremophor RH 40 coagulated above 10% (expressed as a percentage of the mass of the film-forming agent used). Analogous preparations using propylene glycol (PG), PEG6000, and Lutrol F 68, on the other hand, were found to be stable at all concentrations. The instability was not caused by the Kollicoat MAE 30 D polymer dispersion as such, but by interactions between the finely dispersed pigments and other formulation ingredients. Equivalent nonpigmented preparations are stable and do not coagulate. With all the plasticizers investigated, the minimum film-forming temperature (MFT) fell, albeit to differing degrees, as the amount of plasticizer increased. Similarly, the tensile strength of isolated films declined as plasticizer concentration increased, while the reverse was true as regards their elongation at break. Whereas neither the subsequent disintegration time nor the rate of release of active ingredient at pH 6.8 was significantly affected by the various plasticizer additives, the different film-coated tablet formulations with a core containing a powerful disintegrant exhibited varying degrees of permeability to simulated gastric fluid. With PEG6000, permeability increased as the plasticizer concentration increased, while Lutrol F 68 provided an optimum barrier at 20%, and PG provided a good barrier between 10% and 30%. No gastroresistance was obtained with TEC at 10%. Only the best plasticizer formulations were used in the trials with different talc concentrations, namely, those formulations with 20% PEG6000, 20% Lutrol F 68, 20% PG, and 10% PG. When talc was added, the MFT rose, reaching its maximum at 13% talc (as a proportion of the film-forming agent). In the test for gastroresistance, film-coated caffeine tablets without talc absorbed distinctly more acid than those containing talc. Above 27% talc, the acid resistance improved only insignificantly. On the other hand, during this test, only a maximum of 3% of the active ingredient was released into the gastric juice. Of the variants investigated, the formulation with 20% PG and 27% talc performed best.