In 32 ambulant epileptic patients, the plasma levels of diphenylhydantoin were measured gas chromatographically monthly to bimonthly for three years. The mean diphenylhydantoin plasma levels were increased from 6.1 ± 2.9μg/ml during the first year to 11.7 ± 3.3μg/ml during the second and 15.0 ± 2.5μg/ml during the third year. The annual mean number of grand mal seizures per patient decreased from 5.8 to 4.1 and 1.6, respectively.
The optimal diphenylhydantoin plasma levels varied between patients and depended on the severity of the epilepsy. In some cases it was close to or above 20μg/ml. Acute cerebellar side effects were rare and reversible.
The overall data strongly suggest that monitoring of the diphenylhydantoin plasma levels is a valuable aid in the management of patients with generalized epileptic seizures.
Lund L. Anticonvulsant Effect of Diphenylhydantoin Relative to Plasma LevelsA Prospective Three-Year Study in Ambulant Patients With Generalized Epileptic Seizures. Arch Neurol. 1974;31(5):289-294. doi:10.1001/archneur.1974.00490410037002