The level should drop fairly quickly. I take 300 mg twice a day and I'm under 20 mcq/ml. If I miss one dose, I begin to have breakthrough effects.
So many variables between people, their size, age, etc. One thing that I do know about
Phenytoin is that it is heavily metabolized by the liver, usually the Cytochrome P-450 system. Other drugs can interfere with the ability of the liver to adequately remove the Phenytoin, and it can exist in the body at much higher levels if that occurs. Liver disease would also effect metabolism of Phenytoin.
Be absolutely sure that his doctor knows everything he is taking, medication, supplements, cold medicine etc. everything and anything. Phenytoin can also cause other drugs to exist at higher levels due to the same mechanism. My wife pointed out even antacids, such as calcium antacids, can cause elevation of Phenytoin levels. Be sure the doctor knows all he is taking. Pharmacists can also be consulted.
I've taken Phenytoin for 20 years, it's very effective.
Post Edited (JungRulz) : 1/18/2014 6:18:15 AM (GMT-7)