instances have been documented with serum levels above 40 mugm/ml for phenytoin or mephenytoin alone , or above 50 mugm/ml of combined hydantoins phenytoin and mephenytoin , and when the level is in the range of 20 mugm/ml and above for carbamazepine .
C0020209
hydantoins
C0025381
mephenytoin