Phenytoin enteral feed interactions

The interaction of oral phenytoin with enteral feeding formulations has been reviewed (83). Four prospective, randomized, controlled trials in healthy volunteers showed no interaction. However, numerous anecdotal reports and studies have shown dramatic reductions in serum phenytoin concentrations in patients receiving enteral feeding formulations. The authors therefore concluded that this interaction occurs in patients but not in healthy volunteers. 

Au Yeung SC, Ensom MH. Phenytoin and enteral feedings does evidence support an interaction Ann Pharmacother 2000 34(7-8) 896-905. 

A number of methods to minimize the interaction between phenytoin and continuous enteral feeding have been suggested, but no consensus exists. Some clinicians choose holding the feeding for 1 to 2 hours before and after phenytoin administration to minimize the interaction. But since this has not been proven effective and may result in suboptimal nutrition, others choose not to interrupt the feeding. 

Gilbert S, Hatton J, Magnuson B. How to minimize interaction between phenytoin and enteral feedings Two approaches. Nutr Chn Pract 1996 11 28-31. 

A study in 20 patients and 5 healthy subjects found that phenytoin absorption was reduced by about 70% when it was given by nasogastric tube with an enteral feed product (Isocat) at a rate of 100 to 125 mL/hour. Other reports describe the same interaction in patients given Ensure Isocaiydi or Os/nofite. " ... 

Weinryb J, Cogen R. Interaction of nasogastric phenytoin and enteral feeding solution. JAm... 

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