Pulsatile systems are gaining a lot of interest as they deliver the drug at the right site of action at the right time and in the right amount, thus providing spatial and temporal delivery and increasing patient compliance. The basic design of pulsatile drug delivery system consists of formaldehyde treated hard gelatin capsule body, filled with Eudragit microspheres of doxofylline and plugged with a hydrogel polymer. Microspheres were prepared using combination of Eudragit L-100 and S-100 with different core: coat ratios by solvent evaporation technique. Different plugging materials like Xanthan gum, Locust bean gum and Psyllium husk were used in the design of pulsatile capsule. The insoluble hard gelatin body was cap sealed by 5% ethanolic solution of ethylcellulose and then the entire capsule was enteric coated with HPMCP to render the system insoluble in gastric pH. Dissolution studies of the pulsatile drug delivery system revealed the absence if drug release in first three hours and negligible release in the fourth hour and thus a lag time of 3-4 hrs was achieved. In conclusion, time and pH dependent pulsatile drug delivery system was successfully designed, evaluated for various parameters and found satisfactory with respect to the desired lag time which is needed in the chronotherapeutic delivery of doxofylline in the treatment of nocturnal asthma.
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