Disposition of mephenytoin and its metabolite, nirvanol, in epileptic patients.
We investigated the conversion of mephenytoin to nirvanol in five patients with uncontrolled complex partial seizures. After a 50-mg single oral dose, mean peak mephenytoin level was 0.48 microgram/ml and nirvanol 0.37 microgram/ml. After 400 mg, peak mephenytoin level was 3.9 micrograms/ml and nirvanol 2.5 micrograms/ml. On 400 mg daily, mephenytoin reached a mean steady-state level of 1.5 micrograms/ml. Nirvanol mean steady-state level was 18 micrograms/ml. Mean plasma half-life was 17 hours for mephenytoin and 114 hours for nirvanol. Two patients had reduced seizures during mephenytoin therapy and one a transient increase during drug withdrawal. No toxicity was seen, but mephenytoin was not more effective than phenytoin.
D000293:Adolescent; D000328:Adult; D004828:Epilepsies, Partial / Q000097:blood / Q000188:drug therapy*; D005260:Female; D006801:Humans; D006827:Hydantoins / Q000627:therapeutic use*; D008297:Male; D008617:Mephenytoin / Q000031:analogs & derivatives / Q000097:blood / Q000627:therapeutic use*
D006827:Hydantoins; C014544:ethylphenylhydantoin; D008617:Mephenytoin