In recent years, many medical institutions have begun using water-soluble dietary fiber (WSDF) as a deglutition aid to improve oral medication compliance. WSDF has been reported to adsorb carbohydrates and lipids, and lower blood levels of glucose and lipids. Thus, dietary fiber could potentially adsorb drugs in a similar manner, thereby decreasing the amount of a drug absorbed and attenuating its efficacy. In the present study, we used the ultrafiltration method to assess the drug adsorption of three types of WSDFs with different physicochemical properties. Each WSDF was incubated with the various drugs in a 37ºC thermostatic bath for 10, 30, 60, 120, 240, and 360 minutes and then subjected to ultrafiltration to elute the unadsorbed drug, which was measured by HPLC. Glucomannan showed higher drug adsorption than the other types of WSDF. The adsorption of atorvastatin calcium hydrate to glucomannan and pectin was about 60%, which showed almost no change from 10 to 360 minutes after the start of incubation. On the other hand, the adsorption to xanthan gum was increased from 22% at 10 minutes to 47% at 360 minutes. The present results demonstrate that there are cases of time-dependent increases in drug adsorption depending on the WSDF and drug combination.
