No medicine is known to get in the way of the body turning fosphenytoin into phenytoin. However, some medicines can raise the level of phenytoin in the blood. These include amiodarone, chloramphenicol, chlordiazepoxide, cimetidine and other H2 blockers, diazepam, dicumarol, disulfiram, estrogens, ethosuximide and other succinimides, fluoxetine, halothane, isoniazid, methylphenidate, phenothiazines, phenylbutazone, salicylates, sulfonamides, tolbutamide and trazodone. Drinking a large amount of alcohol in one sitting can also raise it.
What should I do?
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.