Serum-phenytoin levels in management of epilepsy.

Steady-state serum-phenytoin levels were measured in five patients whose phenytoin dosage was changed three or more times for therapeutic purposes. Data from four of these patients and from fifteen others have been used to construct a nomogram which permits the clinician, given a single, accurate, steady-state phenytoin level, to adjust the dosage to achieve the desirable therapeutic concentration of 60 or 80 mumol per litre (15 or 20 mug. per ml.).