Phenytoin elimination after intoxication during long-term treatment.

Because of the saturable nature of phenytoin metabolism, intoxication due to overdosage with this drug occurs relatively frequently. The present paper reports on a systematic study of phenytoin elimination in six patients with clinical signs of overdosage and with initial serum phenytoin levels well above the normal therapeutic range (40 mumol/L to 80 mumol/L). On the basis of data obtained, it is recommended that, when a patient presents with symptoms of phenytoin intoxiation, an initial serum phenytoin level should be determined. If this exceeds 130 mumol/L, the drug should be withdrawn for a period of 72 to 84 hours, then the administration should be recommenced at a lower dose.