Enhanced gastrointestinal excretion of phenytoin in a patient with Crohn's disease.

A patient with Crohn's disease and generalized seizures who lacked the distal small bowel and ascending colon required 600 mg of intravenous phenytoin daily (11 mg/kg/24 h) to maintain her plasma phenytoin levels in the 12-24 micrograms/ml range. She received no oral phenytoin. Stool volumes ranged from 1,125 to 1,875 ml/24 h, and stool fraction phenytoin levels from 15 to 41 micrograms/ml. Urinary 5-(p-hydroxyphenyl)-5-phenylhydantoin and phenytoin levels in three 24-h samples were sufficient to account for 26, 46, and 57% of the administered drug, compared with the expected 70-90%. This was most likely due to an alteration of the normal cycle of absorption and reexcretion between the intestinal lumen and the blood resulting in net excretion of phenytoin into the bowel.