Phenytoin (By mouth)


Phenytoin (FEN-i-toin)
Treats different types of seizures (epilepsy). This medicine is an anticonvulsant.

Brand Name(s)

There may be other brand names for this medicine.

Dilantin Kapseals, Dilantin-125, Dilantin Infatabs, Dilantin, Phenytek, AvPak Extended Phenytoin Sodium, Diphen

When This Medicine Should Not Be Used

You should not use this medicine if you have had an allergic reaction to phenytoin or to similar medicines (such as Cerebyx®, Mesantoin®, or Peganone®), or if you are pregnant.

How to Use This Medicine

Capsule, Long Acting Capsule, Liquid, Chewable Tablet
  • Your doctor will tell you how much of this medicine to use and how often. Do not use more medicine or use it more often than your doctor tells you to.
  • You may take this medicine with food if it upsets your stomach. Take this medicine at the same time each day.
  • Do not change brands or dosage forms of phenytoin without first checking with your doctor. Different products may not work the same way. If you refill your medicine and it looks different, check with your pharmacist.
  • Swallow the capsule whole. Do not open, crush, or chew it.
  • The chewable tablet may be chewed, swallowed whole, or crushed before swallowing.
  • Shake the oral liquid before each use. Measure the oral liquid medicine with a marked measuring spoon, oral syringe, or medicine cup.
  • If you are receiving tube feedings, take phenytoin at least 2 hours before, or 2 hours after a feeding.
If a dose is missed:
  • If you miss a dose or forget to use your medicine, use it as soon as you can. If it is almost time for your next dose, wait until then to use the medicine and skip the missed dose. Do not use extra medicine to make up for a missed dose.

How to Store and Dispose of This Medicine

  • Store the medicine in a closed container at room temperature, away from heat, moisture, and direct light. Do not freeze the oral liquid.
  • Ask your pharmacist, doctor, or health caregiver about the best way to dispose of any leftover medicine after you have finished your treatment. You will also need to throw away old medicine after the expiration date has passed.
  • Keep all medicine away from children and never share your medicine with anyone.

Drugs and Foods to Avoid

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.
  • There are many other drugs that can interact with phenytoin. Make sure your doctor knows about all other medicines you are using.
  • Make sure your doctor knows if you are also using amiodarone (Cordarone®), chloramphenicol (Chloromycetin®), chlordiazepoxide (Librium®), diazepam (Valium®), disulfiram (Antabuse®), halothane (Fluothane®), isoniazid (Nydrazid®), methylphenidate (Ritalin®), ticlopidine (Ticlid®), tolbutamide (Orinase®), medicine to treat seizures (such as carbamazepine, ethosuximide, methsuximide, phenobarbital, sodium valproate, valproic acid, Depakene®, Luminal®, Tegretol®, or Zarontin®), medicine to treat depression (such as amitriptyline, doxepin, fluoxetine, nortriptyline, paroxetine, trazodone, Desyrel®, Prozac® or Sinequan®), a stomach medicine (such as cimetidine, ranitidine, Tagamet®, or Zantac®), or a blood thinner (such as dicumarol, warfarin, or Coumadin®).
  • Tell your doctor if you are also using aspirin, doxycycline (Vibramycin®), molindone (Moban®), phenylbutazone, reserpine, rifampin (Rifadin®, Rimactane®), sucralfate (Carafate®), theophylline (Theo-Dur®), Vitamin D, medicine for heart problems (such as digitoxin, furosemide, quinidine, or Lasix®), a steroid medicine (such as dexamethasone, prednisolone, prednisone, or Medrol®), or a phenothiazine medicine (such as prochlorperazine, Compazine®, Mellaril®, Phenergan®, Thorazine®, or Trilafon®).
  • If you are using an antacid (Maalox® or Mylanta®), take it least 1 hour after you take phenytoin.
  • Birth control pills may not work while you are using phenytoin. To keep from getting pregnant, use another form of birth control such as condoms, a diaphragm, or contraceptive foam or jelly.
  • Do not drink alcohol while you are using this medicine.

Warnings While Using This Medicine

  • Using this medicine while you are pregnant can harm your unborn baby. Use an effective form of birth control to keep from getting pregnant. If you think you have become pregnant while using the medicine, tell your doctor right away. Your doctor may want you to join a pregnancy registry for patients taking a seizure medicine.
  • Make sure your doctor knows if you are breastfeeding, or if you have kidney disease, liver disease, lymph node problem (such as lymphadenopathy), bone problem (such as osteoporosis), an enzyme problem (such as porphyria), or diabetes.
  • Do not stop using this medicine suddenly without asking your doctor. You may need to slowly decrease your dose before stopping it completely.
  • For some children, teenagers, and young adults, this medicine can increase thoughts of suicide. Tell your doctor or your child's doctor right away if you or your child start to feel more depressed and have thoughts about hurting yourselves. Report any unusual thoughts or behaviors that trouble you or your child, especially if they are new or get worse quickly. Make sure the doctor knows if you or your child have trouble sleeping, get upset easily, have a big increase in energy, or start to act reckless. Also tell the doctor if you or your child have sudden or strong feelings, such as feeling nervous, angry, restless, violent, or scared. Let the doctor know if you, your child, or anyone in your family has bipolar disorder (manic-depressive) or has tried to commit suicide.
  • If you develop a skin rash, hives, or any allergic reaction to this medicine, stop taking the medicine and check with your doctor as soon as possible.
  • Your doctor will need to check your blood at regular visits while you are using this medicine. Be sure to keep all appointments.
  • This medicine may raise or lower your blood sugar, or it may cover up symptoms of very low blood sugar (hypoglycemia).
  • Make sure any doctor or dentist who treats you knows that you are using this medicine. This medicine may affect the results of certain medical tests.
  • Brush your teeth, use dental floss, and see a dentist on a regular basis. All of these things can help avoid gum bleeding or enlargement.
  • This medicine may make you drowsy. Avoid driving, using machines, or doing anything else that could be dangerous if you are not alert.

Possible Side Effects While Using This Medicine

Call your doctor right away if you notice any of these side effects:
  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing.
  • Blistering, peeling, red skin rash.
  • Dark-colored urine or pale stools.
  • Feeling confused, nervous, or irritable.
  • Fever, chills, cough, sore throat, and body aches.
  • Lumps in your armpits, neck, hands, or thighs.
  • Nausea, vomiting, loss of appetite, or pain in your upper stomach.
  • Numbness, tingling, or burning pain in your hands, arms, legs, or feet.
  • Problems with balance or walking.
  • Severe confusion or unsteadiness.
  • Slurred speech.
  • Tremors.
  • Uncontrolled eye or body movements.
  • Unusual bleeding, bruising, or weakness.
  • Yellowing of your skin or the whites of your eyes.
If you notice these less serious side effects, talk with your doctor:
  • Constipation.
  • Drowsiness or dizziness.
  • Excess hair growth.
  • Headache.
  • Mild rash.
  • Trouble with sleeping.

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088
Review Date: 2011-02-04 Reviewed By: Keywords: ,
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