BIOPHARMACEUTICAL EVALUATION OF TIME-CONTROLLED PRESS-COATED TABLETS CONTAINING POLYMERS TO ADJUST DRUG-RELEASE

This paper deals with press-coated modified release tablets in which t he drug dose is situated in the core or is divided between the core an d the coat. The coat contains polymer (sodium alginate pr hydroxypropy lmethyl cellulose, HPMC) to control drug release. The main objective w as to investigate how the pharmacokinetic profile of the model drug co uld be modified by altering the proportion of the drug between the cor e and the coat. The effect of the amount of the polymer in the coat wa s also studied. Bioavailability tests were carried out on healthy volu nteers. In the absorption curves of the tablets containing 50%, 67% an d 80% of the drug in the core and 180 mg HPMC in the coat a bimodal pr ofile was observed. No bimodal release pattern in the in vitro dissolu tion studies was found. If the whole dose was incorporated in the core the absorption curve has only one clear t(max) value at about 10 h. D oubling the amount of HPMC in the coat dramatically decreased drug abs orption. It was concluded that, if a slightly reduced t(max)-value was required, the viscosity grade of HPMC used should be lowered.