An easy producible new oral hydrocolloid drug delivery system with a late burst in the release profile

One of the main drawbacks of hydrocolloid matrices as oral controlled drug delivery systems is the often observed decreasing rate of drug release at the end of the release process. This study describes a new pH-controlled hydrocolloid drug delivery system consisting of a neutral cellulose ether as basis polymer and enteric coating materials as additives. The new dosage form is able to accelerate the drug release at a predetermined pH. In a typical example, methylhydroxy ethylcellulose, MHEC 10000 B, was used as the basis polymer and hydroxypropyl methylcellulose acetate succinate, HPMCAS HF, as release modifier. The new delivery system is characterized by its homogeneous structure and easy production by direct compression of the components. The acceleration is well reproducible. Furthermore the new formulation shows high stability against hydrodynamic stress and tolerates ionic strengths up to 0.25 without any significant changes in the release profile. As mechanism of the final burst at pH values >5.7, enforced erosion of the gel layer surrounding the tablet core, could be identified.