Meds causing seziures

I take Dilantin for what I believe is a seizure disorder. The only time I have had problems is if my dilantin level drops. Recently I had a seizure and my Dilantin level was 5.5. Was this seizure caused from the dilantin or was it a true seizure. If anyone was taking this medication and the level dropped would it cause anyone to have a seizure or only someone that has problems with seizures.

[Arti Sharma, M.D.]

Hi there,
The usual maintenance dose of Dilantin as monotherapy is 4-7 mg/kg per day. A therapeutic blood level of phenytoin 10-20 mcg/mL is considered as normal. Your blood levels are quite low. You may need an increase in dosage. It may be possible that these low drug levels are the cause of your break through seizure. It is best to consult a neurologist and get your doubts clarified. Do keep me posted.
Best luck and regards!