The objective of the study was to prepare delayed release doxycycline hyclate capsules with suitable blend of doxycycline hyclate-coated pellets (DC pellets) and delayed release pellets (DR pellets). Formulation was optimized on the basis of in vitro drug release. DC pellets were prepared to optimize the amount of polyvinyl pyrrolidone and the optimum concentration was found to be 5%. Two batches of DC pellets showed desired release in buffer medium. DR pellets formulation was optimized using polymer and other variables. The blend of DC pellets (75%) and DR pellets (25%) in capsules produced an optimum drug release in acid and buffer media
S. C. Basak, Dr. Kaladhar Kamalasanan, and Subburaj, T., “Studies in Formulation of Delayed Release Capsules of Doxycycline Hyclate”, ACTA Pharmaceutica Sciencia, vol. 48, no. 2, pp. 121- 128, 2006.