Phenytoin Injection

What is this medication?

PHENYTOIN (FEN i toyn) prevents and controls seizures in people with epilepsy. It may also be used to prevent and treat seizures during or after brain surgery. It works by calming overactive nerves in your body.

This medicine may be used for other purposes; ask your health care provider or pharmacist if you have questions.

What should I tell my care team before I take this medication?

They need to know if you have any of these conditions:

• Alcohol use disorder
• Asian ancestry
• Diabetes
• Heart problems
• Liver disease
• Low blood pressure
• Suicidal thoughts, plans, or attempt by you or a family member
• An unusual or allergic reaction to phenytoin, hydantoin, other medications, foods, dyes, or preservatives
• Pregnant or trying to get pregnant
• Breastfeeding

How should I use this medication?

This medication is for injection into a vein. It is given in a hospital or clinic setting.

Talk to your care team about the use of this medication in children. While this medication may be prescribed for selected conditions, precautions do apply.

Overdosage: If you think you have taken too much of this medicine contact a poison control center or emergency room at once.

NOTE: This medicine is only for you. Do not share this medicine with others.

What if I miss a dose?

This does not apply.

What may interact with this medication?

Do not take this medication with any of the following:

• Artemether
• Certain antivirals for HIV or hepatitis
• Idelalisib
• Isavuconazonium
• Lonafarnib
• Lorlatinib
• Lumefantrine
• Lurasidone
• Pacritinib
• Praziquantel
• Ranolazine

This medication may also interact with the following:

• Albendazole
• Alcohol
• Aspirin and aspirin-like medications
• Bleomycin
• Capecitabine
• Carboplatin
• Certain medications for blood pressure, heart disease, irregular heartbeat
• Certain medications for depression, anxiety, or other mental health conditions
• Certain medications for cholesterol, such as atorvastatin, fluvastatin, simvastatin
• Certain medications for fungal infections, such as fluconazole, itraconazole, ketoconazole, miconazole, posaconazole, voriconazole
• Certain medications for seizures, such as carbamazepine, ethosuximide, felbamate, lacosamide, lamotrigine, methsuximide, oxcarbazepine, phenobarbital, topiramate, valproic acid, vigabatrin
• Certain medications for stomach problems, such as antacids, cimetidine, omeprazole, sucralfate
• Certain medications that prevent or treat blood clots, such as warfarin, apixaban, dabigatran, edoxaban, and rivaroxaban
• Chloramphenicol
• Chlorpropamide
• Cisplatin
• Cyclosporine
• Disulfiram
• Doxorubicin
• Doxycycline
• Estrogen or progestin hormones
• Fluorouracil
• Folic acid
• Irinotecan
• Isoniazid
• Medications that relax muscles for surgery
• Methadone
• Methotrexate
• Methylphenidate
• Paclitaxel
• Phenothiazines, such as chlorpromazine, mesoridazine, prochlorperazine, thioridazine
• Rifampin
• St. John's wort
• Steroid medications, such as prednisone or cortisone
• Sulfadiazine
• Sulfamethoxazole
• Teniposide
• Theophylline
• Ticagrelor
• Ticlopidine
• Tolbutamide
• Vitamin D

This list may not describe all possible interactions. Give your health care provider a list of all the medicines, herbs, non-prescription drugs, or dietary supplements you use. Also tell them if you smoke, drink alcohol, or use illegal drugs. Some items may interact with your medicine.

What should I watch for while using this medication?

Your condition will be monitored carefully while you are receiving this medication.

This medication may cause serious skin reactions. They can happen weeks to months after starting the medication. Contact your care team right away if you notice fevers or flu-like symptoms with a rash. The rash may be red or purple and then turn into blisters or peeling of the skin. You may also notice a red rash with swelling of the face, lips, or lymph nodes in your neck or under your arms.

This medication may affect your coordination, reaction time, or judgment. Do not drive or operate machinery until you know how this medication affects you. Sit up or stand slowly to reduce the risk of dizzy or fainting spells. Drinking alcohol with this medication can increase the risk of these side effects.

This medication may cause thoughts of suicide or depression. This includes sudden changes in mood, behaviors, or thoughts. These changes can happen at any time but are more common in the beginning of treatment or after a change in dose. Call your care team right away if you experience these thoughts or worsening depression.

This medication may cause a decrease in vitamin D and folic acid. You should make sure that you get enough vitamins while you are taking this medication. Discuss the foods you eat and the vitamins you take with your care team.

What side effects may I notice from receiving this medication?

Side effects that you should report to your care team as soon as possible:

• Allergic reactions—skin rash, itching, hives, swelling of the face, lips, tongue, or throat
• High blood sugar (hyperglycemia)—increased thirst or amount of urine, unusual weakness or fatigue, blurry vision
• Infection—fever, chills, cough, or sore throat
• Liver injury—right upper belly pain, loss of appetite, nausea, light-colored stool, dark yellow or brown urine, yellowing skin or eyes, unusual weakness or fatigue
• Pain, swelling, blue or purple skin color at the injection site that spreads
• Phenytoin toxicity—uncontrollable eye movements, loss of balance or coordination, trouble speaking, unusual weakness or fatigue, nausea, vomiting
• Rash, fever, and swollen lymph nodes
• Redness, blistering, peeling, or loosening of the skin, including inside the mouth
• Slow heartbeat—dizziness, feeling faint or lightheaded, confusion, trouble breathing, unusual weakness or fatigue
• Swollen lymph nodes in the neck, groin, chest, or underarm area
• Thoughts of suicide or self-harm, worsening mood, or feelings of depression
• Unusual bruising or bleeding

Side effects that usually do not require medical attention (report to your care team if they continue or are bothersome):

• Difficulty with paying attention, memory, or speech
• Dizziness
• Drowsiness
• Headache

This list may not describe all possible side effects. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Where should I keep my medication?

Keep out of the reach of children.

Store at room temperature between 15 and 30 degrees C (59 and 86 degrees F). Throw away any unused medication after the expiration date.

NOTE: This sheet is a summary. It may not cover all possible information. If you have questions about this medicine, talk to your doctor, pharmacist, or health care provider.