• Phenytoin, administered by suspension into a feeding tube through which continuous enteral feedings are being given, is very poorly absorbed. There appears to be very little information regarding this potentially serious problem in the general medical literature. Commonly used doses of phenytoin (300 to 500 mg/d) may result in almost undetectable serum levels. Therapeutic phenytoin levels may be obtained if a very large dose of the drug is given. Our patient required 1800 mg daily In two divided doses to get a serum phenytoin level of 9 μg/mL. Commonly used enteral feedings were being delivered by way of a continuous infusion pump. We found one enteral feeding product that did not severely impair the absorption of phenytoin. The mechanism by which enteral feedings Impair phenytoin absorption is unknown.
(Arch Intern Med 1987;147:1821)