Interest in dietary fiber has been growing due to the many benefits it has for health. It is well known that dietary fiber reduces the risk of developing health problems such as obesity, hypertension, constipation, type 2 diabetics and hyperlipidemia. However, dietary fiber is also known to reduce the bioavailability of minerals, nutrients and certain drugs, though the interaction between dietary fiber and drugs is still poorly understood. In this study, we examined the adsorption of drugs (theophylline, acetaminophen, metoprolol, chlorpromazine, imipramine, amitriptyline and diclofenac sodium) onto several types of dietary fiber (cellulose, chitosan, pectin, sodium alginate and glucomannan) at pH 3 and pH 7 in order to determine the in vitro adsorption characteristics of dietary fiber. Our findings indicated that adsorption of drugs onto dietary fiber ranged from 0 to 96%, varying with the types of dietary fiber and drugs, and pH. Chlorpromazine, imipramine and amitriptyline showed particularly marked adsorption onto sodium alginate and glucomannan. We considered that ionic bonding was one of the reasons for adsorption.
These findings indicate the possibility of the bioavailability of drugs being reduced when they are taken with dietary fiber due their adsorption onto dietary fiber.
