No drugs are known to interfere with the conversion of Fosphenytoin to Phenytoin. Drugs that may increase plasma Phenytoin concentrations include: Acute alcohol intake, Amiodarone, Chloramphenicol, Chlordiazepoxide, Cimetidine, Diazepam, Dicumarol, Disulfiram, Estrogens, Ethosuximide, Fluoxetine, H2-Antagonists, Halothane, Isoniazid, Methylphenidate, Phenothiazines, Phenylbutazone, Salicylates, Succinimides, Sulfonamides, Tolbutamide, Trazodone. Drugs that may decrease plasma phenytoin concentrations include: Carbamazepine, chronic alcohol abuse, Reserpine. Drugs that may either increase or decrease plasma Phenytoin concentrations include: Phenobarbital, Valproic Acid, and Sodium Valproate. Similarly, the effects of Phenytoin on Phenobarbital, Valproic Acid and Sodium plasma Valproate concentrations are unpredictable. Potentially Fatal: May cause loss of virologic response and...
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