Amelioration of methotrexate-induced malabsorption by vitamin A.

Methotrexate (MTX) induces damage to the small intestine, resulting in malabsorption and diarrhea. We found that the coadministration of vitamin A (VA) with MTX protected the small intestine from MTX-induced damage. In this study, the permeability of D-glucose, D-xylose and L-leucine through the small intestine of rats treated with MTX and/or VA was studied using everted segments of small intestine. MTX treatment decreased permeability and VA coadministration prevented the decrease. The transport of D-glucose in the small intestine of MTX plus VA- and VA-treated rats and of control rats followed Michaelis-Menten kinetics, in contrast to the transport kinetics in MTX-treated rats. The pharmacokinetics of orally administered [14C]-D-glucose in control rats and MTX- and/or VA-treated rats was also studied. The bioavailability of D-glucose in MTX-treated rats was lower than in the other three groups. VA coadministration improved the bioavailability of D-glucose. Thus, it seems likely that VA ameliorates MTX-induced malabsorption.