Phenytoin

Pronunciation: FEN-i-toin
Generic Name: Phenytoin
Brand Name: Generic only. No brands available.

Phenytoin is to be injected slowly.

Phenytoin is used for:

Treating certain types of seizures (eg, status epilepticus). It is also used to prevent and treat seizures that may occur during or after brain or nervous system surgery. It may also be used for other conditions as determined by your doctor.

Phenytoin is an anticonvulsant. It works in the brain to block the spread of seizure activity.

Do NOT use Phenytoin if:

• you are allergic to any ingredient in Phenytoin or to another hydantoin (eg, fosphenytoin)


• you have certain types of heart problems (eg, very slow heartbeat, certain types of heart block, Adams-Stokes syndrome)


• you are taking cabazitaxel, crizotinib, dronedarone, etravirine, lurasidone, nifedipine, nisoldipine, praziquantel, ranolazine, rilpivirine, rivaroxaban, roflumilast, ticagrelor, or vandetanib

Contact your doctor or health care provider right away if any of these apply to you.

Before using Phenytoin:

Some medical conditions may interact with Phenytoin. Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you:

• if you are pregnant, planning to become pregnant, or are breast-feeding


• if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement


• if you have allergies to medicines, foods, or other substances


• if you have heart problems (eg, heart block), low blood pressure, the blood disease porphyria, liver disease, diabetes, a weakened immune system, bone problems (eg, weak bones, osteoporosis), or a history of lymph gland problems


• if you or a family member has had anticonvulsant hypersensitivity syndrome (AHS)


• if you are in very poor heath


• if you drink alcohol or have a history of alcohol abuse


• if you have been tested and know whether or not you have a gene type called HLA-B*1502


• if you have a history of mental or mood problems (eg, depression), or suicidal thoughts or attempts

Some MEDICINES MAY INTERACT with Phenytoin. Tell your health care provider if you are taking any other medicines, especially any of the following:

• Many other prescription and nonprescription medicines (eg, used for allergic reactions, asthma or other breathing problems, blood thinning, diabetes, infections, inflammation, aches and pains, attention deficit hyperactivity disorder, alcoholism, cancer, high blood pressure, indigestion, irregular heartbeat or other heart problems, hepatitis C, high blood iron levels, high cholesterol, HIV, birth control, hormone replacement, immune system suppression, mental or mood problems, pain, sleep, seizures, stomach or bowel problems), multivitamin products, and herbal or dietary supplements (eg, herbal teas, coenzyme Q10, garlic, ginseng, ginkgo, St. John's wort) may interact with Phenytoin. Ask your doctor or pharmacist if you are unsure if any of your medicines might interact with Phenytoin

This may not be a complete list of all interactions that may occur. Ask your health care provider if Phenytoin may interact with other medicines that you take. Check with your health care provider before you start, stop, or change the dose of any medicine.

How to use Phenytoin:

Use Phenytoin as directed by your doctor. Check the label on the medicine for exact dosing instructions.

• Phenytoin is usually given as an injection at your doctor's office, hospital, or clinic. If you will be using Phenytoin at home, a health care provider will teach you how to use it. Be sure you understand how to use Phenytoin. Follow the procedures you are taught when you use a dose. Contact your health care provider if you have any questions.


• Do not use Phenytoin if it contains particles, is cloudy or discolored, or if the vial is cracked or damaged.


• Do not suddenly stop taking Phenytoin. You may have an increased risk of seizures if you stop taking it. If you need to stop Phenytoin, your doctor will gradually lower your dose.


• Keep this product, as well as syringes and needles, out of the reach of children and pets. Do not reuse needles, syringes, or other materials. Ask your health care provider how to dispose of these materials after use. Follow all local rules for disposal.


• If you miss a dose of Phenytoin, contact your doctor right away.

Ask your health care provider any questions you may have about how to use Phenytoin.

Important safety information:

• Phenytoin may cause dizziness or drowsiness. These effects may be worse if you take it with alcohol or certain medicines. Use Phenytoin with caution. Do not drive or perform other possibly unsafe tasks until you know how you react to it.


• Check with your doctor before you drink alcohol while you are taking Phenytoin. Alcohol may increase or decrease the amount of medicine in your blood.


• Do not change brands or doseforms (eg, tablets, suspension, injection) of Phenytoin without talking with your doctor.


• Do NOT take more than the recommended dose or change your dose without checking with your doctor.


• Patients who take Phenytoin may be at increased risk of suicidal thoughts or actions. The risk may be greater in patients who have had suicidal thoughts or actions in the past. Watch patients who take Phenytoin closely. Contact the doctor at once if new, worsened, or sudden symptoms such as depressed mood; anxious, restless, or irritable behavior; panic attacks; or any unusual change in mood or behavior occur. Contact the doctor right away if any signs of suicidal thoughts or actions occur.


• Proper dental care is important while you are taking Phenytoin. Brush and floss your teeth and visit the dentist regularly.


• Phenytoin may raise your blood sugar. High blood sugar may make you feel confused, drowsy, or thirsty. It can also make you flush, breathe faster, or have a fruit-like breath odor. If these symptoms occur, tell your doctor right away.


• There have been reports of lymph node problems, including cancer, in patients who take Phenytoin. It is not known if Phenytoin may be the cause. Contact your doctor right away if you develop swollen lymph nodes.


• Rarely, a serious and sometimes fatal effect (AHS) has occurred in patients who take Phenytoin. The risk may be higher in black patients and in patients with a weakened immune system. It may also be higher if a patient or family member has had AHS in the past. If this effect occurs, it usually happens within 2 to 4 weeks of starting treatment. However, it has also occurred in patients who have been taking Phenytoin for 3 months or more. Contact your doctor right away if you develop swollen lymph nodes, fever, rash, or symptoms of liver problems (eg, dark urine, loss of appetite, pale stools, stomach pain, yellowing of the skin or eyes).


• Long-term treatment with Phenytoin may cause low blood vitamin D levels. This may increase the risk of low blood calcium or phosphate levels. It may also increase the risk of bone softening, weak bones, or other bone problems (eg, fractures). Discuss any questions or concerns with your doctor.


• Tell your doctor or dentist that you take Phenytoin before you receive any medical or dental care, emergency care, or surgery.


• Hormonal birth control (eg, birth control pills) may not work as well while you are using Phenytoin. To prevent pregnancy, use an extra form of birth control (eg, condoms).


• Patients who have a certain gene type called HLA-B*1502 may have an increased risk of serious skin reactions from Phenytoin. This gene type is found most commonly in Asian patients. Tell your doctor if you have been tested and know whether or not you have the HLA-B*1502 gene type. Discuss any questions or concerns with your doctor.


• Phenytoin may interfere with certain lab tests. Be sure your doctor and lab personnel know you are taking Phenytoin.


• Lab tests, including blood phenytoin levels, liver function, or heart function tests, may be performed while you use Phenytoin. These tests may be used to monitor your condition or check for side effects. Be sure to keep all doctor and lab appointments.


• Use Phenytoin with caution in the ELDERLY; they may be more sensitive to its effects.


• Women who take Phenytoin may experience an increase in seizure activity if they become pregnant. Discuss any questions or concerns with your doctor. If you think you may be pregnant, contact your doctor.


• Phenytoin may cause harm to the fetus. If you may become pregnant, discuss other possible treatment options with your doctor. If a decision is made to take Phenytoin, use effective birth control while you are taking it. Talk with your doctor if you are planning to become pregnant, or if you have questions or concerns about this information.


• PREGNANCY and BREAST-FEEDING: Phenytoin may cause harm to the fetus. If you think you may be pregnant, contact your doctor right away. You will need to discuss the benefits and risks of using Phenytoin while you are pregnant. You and your doctor will need to decide if you will continue to take Phenytoin while you are pregnant. Phenytoin is found in breast milk. Do not breast-feed while using Phenytoin.

Possible side effects of Phenytoin:

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome:

Constipation; dizziness; drowsiness; headache; mild nervousness; nausea; trouble sleeping; vomiting.

Seek medical attention right away if any of these SEVERE side effects occur:

Severe allergic reactions (rash; hives; itching; difficulty breathing or swallowing; tightness in the chest; swelling of the mouth, eyes, face, lips, or tongue); bone pain; burning, numbness, or tingling; butterfly-shaped rash on the face; clumsiness or unsteadiness; confusion; delirium; fast, slow, or irregular heartbeat; new or worsening mental or mood changes (eg, agitation, anxiety, behavior changes, depression, irritability, panic attacks, restlessness, suicidal thoughts or attempts); new or worsening seizures; pain, swelling, or redness at the injection site; red, swollen, blistered, or peeling skin; severe muscle pain; severe or persistent dizziness or drowsiness; severe or persistent trouble sleeping; signs of infection (eg, chills, fever, sore throat); slurred speech; sores in the mouth or around the eyes; swollen lymph nodes; swollen or tender gums; symptoms of liver problems (eg, dark urine, loss of appetite, pale stools, stomach pain, yellowing of the skin or eyes); tremor; trouble walking; unusual bruising or bleeding; unusual eye movements; unusual muscle movements; unusual tiredness or weakness.

This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider. Call your doctor for medical advice about side effects. To report side effects to the appropriate agency, please read the Guide to Reporting Problems to FDA.

See also: Phenytoin side effects (in more detail)

If OVERDOSE is suspected:

Contact 1-800-222-1222 (the American Association of Poison Control Centers), your local poison control center, or emergency room immediately. Symptoms may include confusion; decreased coordination; fainting; loss of consciousness; severe dizziness or headache; severe or persistent nausea or vomiting; slow or difficult breathing; sluggishness; speech problems (eg, slurred speech); tremor; unusual eye movements.

Proper storage of Phenytoin:

Phenytoin is usually handled and stored by a health care provider. If you are using Phenytoin at home, store Phenytoin as directed by your pharmacist or health care provider. Keep Phenytoin out of the reach of children and away from pets.

General information:

• If you have any questions about Phenytoin, please talk with your doctor, pharmacist, or other health care provider.


• Phenytoin is to be used only by the patient for whom it is prescribed. Do not share it with other people.


• If your symptoms do not improve or if they become worse, check with your doctor.


• Check with your pharmacist about how to dispose of unused medicine.

This information is a summary only. It does not contain all information about Phenytoin. If you have questions about the medicine you are taking or would like more information, check with your doctor, pharmacist, or other health care provider.

Issue Date: February 1, 2012

Database Edition 12.1.1.002

Copyright © 2012 Wolters Kluwer Health, Inc.

More Phenytoin resources

• Phenytoin Side Effects (in more detail)
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• Phenytoin Drug Interactions
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• Phenytoin Professional Patient Advice (Wolters Kluwer)


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