In vitro and in vivo effects of selected fibers on the pharmacokinetics of orally administered carbamazepine: Possible interaction between therapeutic drugs and semisolid enteral nutrients.

OBJECTIVE

The management of nutrition using semisolid enteral nutrients is considered useful for avoiding the adverse effects associated with liquid enteral nutrients. In the present study, we used an in vitro analysis to investigate whether carbamazepine (CBZ) is adsorbed by the fibers included in semisolid enteral nutrients. The effects of these fibers on the pharmacokinetic profile of CBZ following its oral administration were also examined in rats.

METHODS

The adsorption of CBZ onto fibers was examined by absorbance monitoring of the filtrate after centrifugation using an ultrafiltration device. Viscosities of each solution were measured by rotational viscosimeter. The CBZ concentration profile after its oral administration (50 mg/kg) was analyzed by a noncompartmental method.

RESULTS

In the two solutions used to reflect gastric juice and fluid in the intestinal tract, CBZ was more strongly adsorbed by water-soluble fibers (guar gum and xanthan gum) than by insoluble fibers (dextrin hydrate). The adsorption of CBZ also was observed even if the concentrations of guar gum and xanthan gum were reduced to such an extent that viscosity was 0 Pa･s. The pharmacokinetic examination of orally administered CBZ revealed that the area under the curve was significantly lower in the guar gum and xanthan gum groups than in the control group.

CONCLUSION

CBZ was adsorbed by fibers used for the semisolidification of enteral nutrients, which may be partially responsible for the alterations observed in the pharmacokinetic profile of CBZ.