Opposite effects of carbohydrate and protein on phenytoin absorption in man.

Food intake has been found to enhance the absorption of phenytoin, as judged from single-dose studies in healthy volunteers taking phenytoin (acid) with and without a standardized breakfast of 1,840 kJ. In order to investigate whether this effect was due to food intake as such or to the ingestion of a certain nutrient, the influence of carbohydrate, fat, and protein, respectively, on phenytoin (acid) absorption was examined in ten healthy volunteers. The nutrients were given separately in amounts corresponding to those of the standardized breakfast previously employed. Phenytoin concentrations in plasma were measured by high-pressure liquid chromatography. The results indicate that, while fat had no measurable influence, carbohydrate may enhance, and protein reduce, the absorption of phenytoin.