Delayed release doxycycline hyclate capsules were prepared with suitable blend of doxycycline hyclate-coated nonpareil seed pellets and doxycycline hyclate delayed release pellets. The delayed release pellets were prepared by coating the doxycycline hyclate-coated pellets with hydroxypropylmethylcellulose phthalate-55 polymer solution. A concentration of polymer in the range of 15 to 20% was found to comply with drug release test as specified in the USP in acid medium but failed to meet the requirements in buffer medium (pH 5.5). The inclusion of sodium starch glycolate (1-3%) in both doxycycline-coated and delayed release pellets preparation stages was found to enhance the release of the drug in the buffer medium without altering its release in acid medium. The blend of delayed release pellets (75%) and drug-coated pellets (25%) in delayed release doxycycline hyclate capsules produced an optimum in vitro drug release in both the media.
S. C. Basak, Dr. Kaladhar Kamalasanan, and Subburaj, T., “Doxycycline hyclate delayed release capsules with sodium starch glycolate as a pH-dependent pore forming agent”, Indian journal of pharmaceutical sciences, vol. 66, no. 5, pp. 704–707, 2004.