Phenytoin Ikapharmindo Drug Interactions

Capsule: Phenytoin effect is enhanced when given along with dicomarol, disulfiram and isoniazid and also if given together with chloramphenicol, halothane, phenyramidol, sulthiamine, viloxasine and thyroid preparations. Phenytoin effects are reduced by the presence of alcohol and phenobarbitone.
Phenytoin may decrease the plasma levels of carbamazepine, valproic acid, etosuksimid and promidon.
Phenytoin is a potent enzyme inductor that can reduce the effectiveness of oral anti-coagulants. antibiotics (doxycycline, rifampicin, chloramfenicol), oral contraceptives, antiarrhythmics (disopiramid, mexiletine, quiridine), digitoxine, analgesics (meperidine, methadone), cyclosporine, corticosteroids and theophylline.
Injection: Drugs which may increase phenytoin serum levels include: Amiodarone, Chloramphenicol, Chlordiazepoxide, Diazepam, Dicumarol, Disulfiram, Halothane, Isoniazid, Methylphenidate, Phenothiazines, Phenylbutazone, Salicylates, Ethosuximide, Sulfonamides, Tolbutamide, Trazodone, Estrogens, H₂-antagonists, acute Alcohol intake.
Drugs which may decrease phenytoin levels include: Carbamazepine, chronic Alcohol abuse, Reserpine and Sucralfate.
Drugs which may either increase or decrease phenytoin serum levels include: Phenobarbital, Sodium Valproate and Valproic Acid.
Although not a true drug interaction, tricyclic antidepressants may precipitate seizures in susceptible patients and phenytoin dosage may need to be adjusted.
Drugs which efficacy is impaired by phenytoin include: Corticosteroids, Coumarin, anticoagulants, Digitoxin, Doxycycline, Furosemide, Quinidine, Rifampin, Theophylline, Estrogens, oral contraceptives and Vitamin D.