Application of acid-treated yeast cell wall (AYC) as a pharmaceutical additive. II: effects of curing on the medicine release from AYC-coated tablets

Acid-treated yeast cell wall (AYC) was newly prepared by acidifying brewers ' yeast cell wall. Core tablets containing 3% of acetaminophen (AAP) were c oated with the AYC aqueous dispersion containing 5% (w/v) of AYC and 0.35% (w/v) of glycerol. The curing of AYC-coated tablets was performed at variou s curing periods of time and temperatures. The effects of curing on AAP rel ease from AYC-coated tablets, the weight and thickness of the coated layer of AYC and the water sorption into the AYC-coated tablets were studied. The tensile strength and pore size distribution of the AYC cast film were meas ured. In the case of 60, 80, or 100 degreesC curing, AAP release from AYC-c oated tablets showed a sigmoidal release profile with an initial lag time. The duration of the lag time increased with the increasing curing time and temperature, though the release rate after the lag time hardly changed. At 120 degreesC curing, the release rate after the lag time decreased with the increasing curing time and a sustained release was observed. The weight an d thickness of the AYC-coated layer and the water sorption rate into AYC-co ated tablets decreased with the increasing curing time and temperature. The tensile strength of the AYC cast film increased with increasing the curing temperature, particularly at 120 degreesC curing. It is considered that th e water was evaporated from the AYC-coated layer and the adhesion force bet ween AYC particles increased during curing, making the structure of the AYC -coated layer densely firm. The changes in the duration of lag time and the release rate may be due to changes in the structure of the AYC-coated laye r caused by curing. These results show that it is feasible to control the l ag time and the release rate of AAP from AYC-coated tablets by varying the curing time and temperature. (C) 2000 Elsevier Science Ireland Ltd. All rig hts reserved.