Interaction between phenytoin and enteral nutrients and its influence on gastrointestinal absorption

The gastrointestinal absorption of phenytoin (PHT), an antiepileptic drug, is often affected by its interaction with co-administered enteral nutrients through a nasogastric (NG) tube, resulting in decreased plasma PHT concentration. In this study, we measured the recovery rate (%) of PHT (Aleviatin^® powder) passed through an NG tube when co-administered with distilled water or enteral nutrients (F2α^®, Racol^® NF, Ensure Liquid^® and Renalen^® LP). We also measured plasma PHT levels in rats, after oral co-administration of PHT with enteral nutrients. We demonstrate that PHT recovery rate was close to 100 % in all cases after passage through the NG tube. In the rat study, the AUC_0→∞ of PHT concentration after oral administration significantly decreased when it was co-administered with F2α^® and Racol^® NF compared to distilled water. However, the AUC_0→∞ of PHT was unchanged when co-administered with F2α^® 2 h after initial PHT administration. We therefore conclude that the co-administration of PHT with F2α^® and Racol^® NF caused a reduction in the absorption of PHT from the gastrointestinal tract to the blood, without adsorption to the NG tube. The administration of enteral nutrients 2 h after PHT is one clear way to prevent a decrease in plasma PHT concentration.