Effect of simultaneously ingested milk on phenytoin bioavailability.

Adverse gastrointestinal symptoms from milk may reduce the bioavailability of phenytoin. In a prospective crossover study, we studied the effect of simultaneous ingestion of phenytoin and milk in 12 patients with partial epilepsy and no adverse gastrointestinal symptoms. Serum phenytoin levels were measured at the start of the study and after 2 weeks. Patients then switched regimens, and a third phenytoin level was determined 2 weeks later. Serum phenytoin levels were similar for patients taking phenytoin with either milk or water.