Time-controlled release by the incorporation of superdisintegrants within the coat of zein dry coated tablets

The aim of this work was to develop zein-based press coated tablets for delayed, time-controlled drug release. Press coated tablets containing dextrates and chlorpheniramine maleate (BCS class 1 drug) in the core, and zein and either NaCl, sodium starch glycolate (SSG) or crospovidone (XPVP) in the coat were produced. Results show that tablets containing zein and NaCl in the coating could not release nearly any drug over 8 h. On the contrary, when SSG and XPVP were incorporated at a level of 8 % in the coating, a delayed drug release pattern was obtained, characterised by a lag-time of 3 h, followed by a burst of >80 % drug release over 6–7 h. Drug release was dependent on the concentration of SSG and XPVP in the formulations. Images of the tablets showed that during the lag-time the dosage forms did not change shape, although they started to swell. After this time, tablets gradually deformed and eventually ruptured. The lag-time is due to the time needed for the water to diffuse in, for the drug to dissolve and for the coating to become sufficiently permeable. The addition of the hydrophilic and swellable superdisintegrants SSG and XPVP to zein shifted the hydrophilic/hydrophobic balance of the coatings to higher hydrophilicity, thus enabling rapid hydration and drug release after the lag-time. This study demonstrates that zein-based macroscopic drug delivery systems can be tuned to tailor drug release to specific needs, i.e. delayed release in this case.