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The objective of the present study was to correlate the results of the in vitro release of a previously reported pulsatile drug delivery system with the in vivo radio imaging study. The formulated drug delivery system containing pellets of barium sulphate was administered to rabbits after overnight fast. Formulated dosage form, previously evaluated for in vitro drug release study, showed drug release after 6-10 h of lag time depending on the hardness as well as the thickness of the plug. Radio imaging study also showed that the plug in the capsule drug delivery system remains intact for the period of 6 h. Thus, the formulated drug delivery system is capable of delaying release in vitro as well as in rabbits for 6 hours.

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.

The aim of the present investigation was to develop a pulsatile drug delivery system based on an insoluble capsule body filled with theophylline microspheres and sealed with a swellable novel polymer plug isolated from the endosperm of seeds of higher plant Delonix regia family-Fabaceae. Theophylline microspheres were prepared by solvent evaporation method using Eudragit S 100. The swellable plugs of varying thickness and hardness were prepared by direct compression, which were then placed in the capsule opening. The drug delivery system was designed to deliver the drug at such a time when it was needed most to offer convenience to the chronic patients of asthma. Formulated dosage forms were evaluated for an in vitro drug release study, which showed that the release might be consistent with a release time expected to deliver the drug to the colon depending on the thickness and hardness of the hydrogel plug. Thus, thickness and hardness of the novel polymeric plug plays an important role in controlling the drug release from the formulated drug delivery system.