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Phenytoin (Dilantin)

How does this medicine work?

Phenytoin (fen-ih-toyn) is most often used to help control seizures.

How should I give it?

Phenytoin comes in liquid, capsule, and tablet form. Give it at regular times to keep a steady level in the bloodstream. Your
child should be awake and alert when taking any medicine. Follow the checked instructions below:

___ If using the liquid form, shake well right before using. Draw up the correct amount in the medicine dropper or oral syringe. Give a small squirt of the medicine inside the cheek. To avoid choking, let your child swallow each squirt before giving more.

___ If the prescription is a capsule it must be swallowed whole.

___ If the prescription is a tablet it can be swallowed whole or chewed. It can also be crushed between 2 spoons or inside a plastic bag or folded paper, and mixed with a very small amount of soft food such as applesauce, ice cream, or jelly. Make sure your child takes all of the mixture.

Are there any precautions about food or other medicines?

Phenytoin can be given with or without food. However, if your child is taking tube feedings, it is important to keep the phenytoin and tube feedings at the same time every day, to keep the blood level steady.

Avoid all food and beverages containing alcohol.

Check with the doctor or pharmacist before giving any other prescription or non-prescription medicines, herbs, or vitamins.

Long use of phenytoin can decrease the levels of vitamins D, K, and folic acid in the body. Include good sources of these vitamins in your child's diet. (If your child is on chemotherapy, check with the oncologist because folic acid may affect the growth of cancer cells.)

Foods high in vitamin D:

  • fortified milk and yogurt
  • fortified breakfast cereal
  • fortified margarine
  • infant formula

Foods high in vitamin K:

  • green leafy vegetables
  • infant formula
  • liver
  • soybean oil
  • whole wheat products

Foods high in folic acid:

  • dried beans and legumes
  • green vegetables
  • infant formula
  • liver
  • nuts
  • oranges

For information on other foods that contain these vitamins, or if you have questions, ask the doctor or dietician.

What should I do if a dose is missed?

If one dose is missed, give it as soon as remembered. Never give a double dose.

If your child vomits (throws up) within 30 minutes after receiving a dose, give it again. If your child vomits the second dose, do not repeat it again.

Call the doctor if your child misses or vomits 2 doses in a row.

What are the side effects?


  • swelling or tenderness of the gums (see below)
  • drowsiness
  • nausea (upset stomach); loss of appetite
  • vomiting (throwing up)
  • constipation (hard bowel movements)
  • decreased coordination (possible clumsiness)


  • insomnia (trouble sleeping)
  • enlarged breasts
  • increased blood sugar
  • low blood counts


  • liver damage

If your child has sore or swollen gums, brush and floss your child's teeth carefully. Massage sore gums or use a cool teething ring. See a dentist regularly.

When should I call the clinic?

  • change in seizure pattern
  • confusion
  • clumsiness
  • red or purple spots on the skin
  • shaking
  • sore throat
  • unusual bruising or bleeding
  • vision problems
  • yellow color in the eyes or skin
  • signs of allergic reaction
    - rash or hives
    - itching
    - wheezing
    - trouble breathing - call 911

What else do I need to know?

Never stop this medicine unless your doctor tells you to stop. Blood samples will be needed to be sure the dose is correct. Remember to schedule it to be done just before a dose is due.

You and your child should know the names of all the medicines he or she is taking. Share this information with anyone involved in your child's care.

Always make sure you have enough medicine on hand. Each time you refill your prescriptions, check to see how many refills are left. If no refills are left, the pharmacist will need 2 or 3 days to contact the doctor to renew the prescription.

Before giving the first dose, read the label. Be sure it is what was prescribed. After a refill, if the medicine looks different to you, ask your pharmacist about it before giving it.

Check the label and expiration date before giving each dose. Ask your pharmacist what to do with outdated or unused medicines. If there is no "take-back" program empty them into the trash.

Store all medicines in their original container and away from direct sunlight or heat. Do not store in humid places such as the bathroom. Keep them out of children's reach, locked up if possible.

If too much or the wrong kind of medicine is taken, call Poison Control (toll-free 1-800-222-1222). If your child is unconscious or has a seizure, call 911.


This sheet is not specific to your child but provides general information. If you have any questions, please call the doctor or pharmacist.

Children's Hospitals and Clinics of Minnesota
Patient/Family Education
2525 Chicago Avenue South
Minneapolis, MN 55404
Last reviewed 8/2015 ©Copyright

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This page is not specific to your child, but provides general information on the topic above. If you have any questions, please call your clinic. For more reading material about this and other health topics, please call or visit Children's Minnesota Family Resource Center library, or visit

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