Improved drug delivery to the lower intestinal tract with tablets compression-coated with enteric/nonenteric polymer powder blends.

The objective of this study was to develop pH-erosion-controlled compression-coated tablets for potential colonic drug delivery with improved gastric resistance and pulsatile release based on compression-coatings of powder blends of the enteric polymer Eudragit® L100-55 and the extended release polymer ethylcellulose. Tablet cores containing model drugs of varying solubilities (acetaminophen, carbamazepine and chlorpheniramine maleate) were compression-coated with different ratios of Eudragit® L100-55:ethylcellulose 10cP FP at different compression forces and tablet core:compression-coat ratios. The compression-coated tablets were characterized by drug release, media uptake, erosion behaviour and wettability. All drugs were released in a pulsatile fashion in higher pH-media after a lag time, which was controlled by the erosion properties of the Eudragit L:ethylcellulose compression-coating. The addition of ethylcellulose avoided premature drug release in lower pH-media and significantly increased the lag time in higher pH-media because of a reduction in wettability, media uptake and erosion of the compression-coatings. Importantly, ethylcellulose also reduced the pH-dependency of the erosion process between pH 5.5 and 7.4. The lag time could also be increased by increasing the compression force and decreasing the core:compression-coat ratio. In conclusion, tablets compression-coated with blends of Eudragit L and ethylcellulose resulted in excellent release properties for potential targeting to the lower intestinal tract with no release in lower pH-media and rapid release after a controllable lag time in higher pH-media.