Formulation and evaluation of a pulsatile drug delivery system using time- and pH-dependant polymers.

The aim of the present study was to develop fast-release enteric-coated tablets for pulsatile drug delivery to the colon. The novelty of this work is a combination of pH- and time-dependant enteric polymers as a single coating. Eudragit S100 was used as a pH-dependant polymer and eudragit RL100 was used as a time-dependant polymer. Theophylline was taken as a model drug. Dissolution studies of enteric-coated tablets were performed with different media having a pH of 1.2, 7.4, and 6.8. Results of the dissolution data show that drug release in the colon could be controlled by using eudragit RL100 eudragit S100. The lag time prior to the drug release was highly affected by a combination of two factors: The percentage of eudragit RL100 and coating level. The optimum formulation was found to be one containing eudragit RL100 and eudragit S100 with a ratio of 60:40 of polymer and coating level of 4.66% w/w. The present study demonstrates that the theophylline enteric-coated tablets could be successfully formulated as a pulsatile drug delivery by the design of a time- and pH-dependant modified chronopharmaceutical formulation. In conclusion, pulsatile drug release over a period of 2-12 hours, consistent with the requirements for chronopharmaceutical drug delivery, can be achieved by using time- and pH-dependant polymers.