phenytoin (generic name)

It is used to control seizures in certain types of epilepsy.
(FEN i toyn)
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What is this medicine?

PHENYTOIN (FEN i toyn) is used to control seizures in certain types of epilepsy.

What should I tell my health care provider before I take this medicine?

They need to know if you have any of these conditions:
  • an alcohol abuse problem
  • Asian ancestry
  • blood disorders or disease
  • diabetes
  • heart problems
  • kidney disease
  • liver disease
  • porphyria
  • receiving radiation therapy
  • suicidal thoughts, plans, or attempt; a previous suicide attempt by you or a family member
  • thyroid disease
  • an unusual or allergic reaction to phenytoin, other medicines, foods, dyes, or preservatives
  • pregnant or trying to get pregnant
  • breast-feeding

How should I use this medicine?

Take this medicine by mouth. Follow the directions on the prescription label. Shake the bottle well before each dose. Use a specially marked spoon or dropper to measure your medicine. Ask your pharmacist if you do not have one. Household spoons are not accurate. Take this medicine with food if it upsets your stomach. Take your doses at regular intervals. Do not take your medicine more often than directed. Do not stop taking this medicine suddenly. This increases the risk of seizures. Your doctor will tell you how much medicine to take. If your doctor wants you to stop the medicine, the dose will be slowly lowered over time to avoid any side effects.


Talk to your pediatrician regarding the use of this medicine in children. Special care may be needed.

What if I miss a dose?

If you miss a dose, take it as soon as you can. If it is almost time for your next dose, take only that dose. Do not take double or extra doses.

What may interact with this medicine?

Do not take this medicine with any of the following medications:
  • delavirdine

This medicine may also interact with the following medications:

  • alcohol
  • aspirin and aspirin-like medicines
  • barbiturate medicines for inducing sleep or treating seizures
  • calcium supplements
  • carbamazepine
  • chloramphenicol
  • chlordiazepoxide
  • cimetidine or other medicines for heartburn or stomach ulcers
  • corticosteroid hormones such as prednisone or cortisone
  • diazepam
  • disulfiram
  • doxycycline
  • enteral feedings (liquid nutritional drinks or tube feeding liquids)
  • ethosuximide
  • female hormones, including contraceptive or birth control pills
  • furosemide
  • halothane
  • isoniazid
  • medicines for mental depression, anxiety or other mood problems
  • medicines to control heart rhythm
  • methsuximide
  • methylphenidate
  • molindone
  • phenylbutazone
  • reserpine
  • rifampin, rifabutin or rifapentine
  • sucralfate
  • sulfonamides like Azulfidine or Bactrim
  • theophylline
  • ticlopidine
  • tolbutamide
  • valproic acid
  • vitamin D
  • warfarin

What should I watch for while using this medicine?

Visit your doctor or health care professional for regular checks on your progress. This medicine needs careful monitoring. Your doctor or health care professional may schedule regular blood tests.

Wear a medical ID bracelet or chain, and carry a card that describes your disease and details of your medicine and dosage times.

Do not change brands or dosage forms of this medicine without discussing the change with your doctor or health care professional.

You may get drowsy or dizzy. Do not drive, use machinery, or do anything that needs mental alertness until you know how this medicine affects you. Do not stand or sit up quickly, especially if you are an older patient. This reduces the risk of dizzy or fainting spells. Alcohol may interfere with the effect of this medicine. Avoid alcoholic drinks.

Birth control pills may not work properly while you are taking this medicine. Talk to your doctor about using an extra method of birth control.

This medicine can cause unusual growth of gum tissues. Visit your dentist regularly. Problems can arise if you need dental work, and in the day to day care of your teeth. Try to avoid damage to your teeth and gums when you brush or floss your teeth.

Do not take antacids at the same time as this medicine. If you get an upset stomach and want to take an antacid or medicine for diarrhea, make sure there is an interval of 2 to 3 hours before or after you took your phenytoin.

The use of this medicine may increase the chance of suicidal thoughts or actions. Pay special attention to how you are responding while on this medicine. Any worsening of mood, or thoughts of suicide or dying should be reported to your health care professional right away.

Women who become pregnant while using this medicine may enroll in the North American Antiepileptic Drug Pregnancy Registry by calling 1-888-233-2334. This registry collects information about the safety of antiepileptic drug use during pregnancy.

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Last Updated: July 21, 2009
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