Sizaject Fosphenytoin Sodium Phenobarbitone
ModeratePhenobarbitone (phenobarbital) can either raise or lower the level of phenytoin in the blood when it is taken with fosphenytoin sodium, since the body turns fosphenytoin into phenytoin. The effect goes the other way too, because phenytoin's effect on phenobarbital levels is unpredictable.
These medicines are often taken together with some care. Your doctor may change a dose, space them apart or check on you more often. Make sure your doctor and pharmacist know you take both.