Phenytoin is used to control seizures (convulsions) in the treatment of epilepsy. It is also used to prevent and treat seizures that occur during brain surgery. This medicine is an anticonvulsant that works in the brain tissue to stop seizures.

This medicine is available only with your doctor's prescription.

Take this medicine only as directed by your doctor. Do not take more of it, do not take it more often, and do not take it for a longer time than your doctor ordered.

This medicine should come with a Medication Guide. Read and follow these instructions carefully. Ask your doctor if you have any questions.

This medicine may be used with other seizure medicines. Keep using all of your seizure medicines unless your doctor tells you otherwise.

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 tablet whole or chew it thoroughly before swallowing it together with a glass of water.

Measure the oral suspension with a marked measuring spoon, oral syringe, or medicine cup. Rinse the dosing spoon or cup with water after each use.

If you are receiving tube feeding preparations, it is best to take this medicine before or after a feeding.

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

More common

Decreased coordination

mental confusion

nervousness

slurred speech

trouble with breathing, speaking, or swallowing

unsteadiness, trembling, or other problems with muscle control or coordination

Rare

Inability to move the eyes

increased blinking or spasms of the eyelid

shakiness and unsteady walk

shakiness in the legs, arms, hands, or feet

sticking out of the tongue

trembling or shaking of the hands or feet

twitching, twisting, or uncontrolled repetitive movements of the tongue, lips, face, arms, or legs

uncontrolled twisting movements of the neck, trunk, arms, or legs

unusual facial expressions

Incidence not known

Bleeding gums

blistering, peeling, or loosening of the skin

blisters, hives, itching, skin rash

bloating of the abdomen or stomach

blood in the urine or stools

bloody, black, or tarry stools

chest pain or discomfort

chills

cough

dark urine

diarrhea

difficulty with moving

fainting spells

fever with or without chills

general feeling of discomfort or illness

general feeling of tiredness or weakness

hair loss

headache

high fever

hoarseness

irritation in the mouth

joint or muscle pain

light-colored stools

lightheadedness or dizziness

lower back or side pain

muscle stiffness

nausea

numbness, tingling, or pain in the hands or feet

painful or difficult urination

pale skin

pinpoint red spots on the skin

red skin lesions, often with a purple center

red, irritated eyes

redness and swelling of the gums

slow or irregular heartbeat

sore throat

sores, ulcers, or white spots on the lips or in the mouth

stomach pain

swollen, painful, or tender lymph glands in the neck, armpit, or groin

unusual bleeding or bruising

unusual tiredness or weakness

upper right abdominal or stomach pain

vomiting

weight loss

yellow eyes or skin

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

Trouble sleeping

uncontrolled eye movements

Incidence not known

Difficulty having a bowel movement

enlarged lips

feeling of constant movement of self or surroundings

increased hair growth on the forehead, back, arms, or legs

pain of the penis on erection

sensation of spinning

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

It is very important that your doctor check your or your child's progress at regular visits while using this medicine to see if it is working properly and to allow for a change in the dose. Blood and urine tests may be needed to check for any unwanted effects.

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.

Do not use this medicine if you or your child are also using delavirdine (Rescriptor®). Using these medicines together may cause unwanted effects.

Lymph node problems may occur while using this medicine. Check with your doctor right away if you or your child have swollen, painful, or tender lymph glands in your neck, armpit, or groin.

Do not stop using this medicine without first checking with your doctor. Your doctor may want you or your child to gradually reduce the amount you are using before stopping completely.

This medicine may cause serious allergic reactions, including angioedema. These can be life-threatening and require immediate medical attention. Tell your doctor right away if you or your child have a rash, itching, hoarseness, trouble breathing, trouble swallowing, or any swelling of your hands, face, or mouth after using this medicine.

Serious skin reactions can occur with this medicine. Check with your doctor right away if you or your child have blistering, peeling, or loose skin, red skin lesions, severe acne or skin rash, sores or ulcers on the skin, a fever, or chills while you are using this medicine.

Tell your doctor right away if you or your child develop a fever, rash, swollen, painful, or tender lymph glands in the neck, armpit, or groin, unusual bleeding or bruising, or yellow eyes or skin after using this medicine. These may be symptoms of a serious and life-threatening condition called drug reaction with eosinophilia and systemic symptoms (DRESS).

Phenytoin may cause heart problems, including a slow heartbeat. Check with your doctor right away if you have chest pain, dizziness, or tiredness.

This medicine may cause liver damage. Check with your doctor right away if you have pain or tenderness in the upper stomach, pale stools, dark urine, loss of appetite, nausea, vomiting, or yellow eyes or skin.

Phenytoin can temporarily lower the number of white blood cells in your blood, increasing the chance of getting an infection. It can also lower the number of platelets, which are necessary for proper blood clotting. If this occurs, there are certain precautions you can take, especially when your blood count is low, to reduce the risk of infection or bleeding:

If you can, avoid people with infections. Check with your doctor immediately if you think you are getting an infection or if you get a fever or chills, cough or hoarseness, lower back or side pain, or painful or difficult urination.
Check with your doctor immediately if you notice any unusual bleeding or bruising, black, tarry stools, blood in the urine or stools, or pinpoint red spots on your skin.
Be careful when using a regular toothbrush, dental floss, or toothpick. Your medical doctor, dentist, or nurse may recommend other ways to clean your teeth and gums. Check with your medical doctor before having any dental work done.
Do not touch your eyes or the inside of your nose unless you have just washed your hands and have not touched anything else in the meantime.
Be careful not to cut yourself when you are using sharp objects such as a safety razor or fingernail or toenail cutters.
Avoid contact sports or other situations where bruising or injury could occur.
This medicine may decrease bone mineral density. A low bone mineral density can cause weak bones or osteoporosis. If you or your child have any questions about this ask your doctor.

This medicine may affect blood sugar levels. If you or your child notice a change in the results of your blood or urine sugar tests or if you have any questions, check with your doctor.

This medicine may cause some people to be agitated, irritable, or display other abnormal behaviors. It may also cause some people to have suicidal thoughts and tendencies or to become more depressed. If you, your child, or your caregiver notice any of these side effects, tell your or your child's doctor right away.

In some patients (usually younger patients), tenderness, swelling, or bleeding of the gums (gingival hyperplasia) may appear soon after phenytoin treatment is started. To help prevent this, brush and floss your teeth carefully and regularly and massage your gums. Also, see your dentist every 6 months to have your teeth cleaned. If you have any questions about how to take care of your teeth and gums, or if you notice any tenderness, swelling, or bleeding of your gums, check with your doctor or dentist.

Before you have any medical tests, tell the medical doctor in charge that you or your child are taking this medicine. The results of some tests may be affected by this medicine.

This medicine may cause drowsiness, trouble thinking, or trouble in controlling movements. Do not drive or do anything else that could be dangerous until you know how this medicine affects you.

Avoid drinking alcohol while you are using this medicine.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.