Phenytoin

💊 What is Phenytoin used for?

• •The label says phenytoin is used to treat generalized tonic-clonic (grand mal) seizures and complex partial (psychomotor, temporal lobe) seizures. It is also used to prevent and treat seizures that happen during or after neurosurgery.

How it works

How it is usually taken

• •The label says the chewable tablet can be chewed thoroughly before swallowing or swallowed whole. It is not meant to be taken once a day. The dose is adjusted for each person, and the label says blood level tests may be needed to guide dose changes. Follow the instructions from your prescriber or pharmacist.

Comes as

• •50 mg yellow, round, scored chewable tablets with banana flavor

⚠️ Phenytoin side effects

🛑 Who should not take Phenytoin, and who should be careful

The label says not to take it if

• 🚨You are allergic to phenytoin or any of its ingredients.
• 🚨You have had a past allergic reaction to CEREBYX (fosphenytoin), PEGANONE (ethotoin), or MESANTOIN (mephenytoin), or to other hydantoins.
• 🚨You have had liver problems from taking phenytoin.
• 🚨You take delavirdine. The label says this combination should not be used.

Tell your doctor before taking it if

• •Tell your healthcare provider if you have ever had depression, mood problems, or suicidal thoughts or behavior.
• •Tell your provider if you have had an allergic reaction to similar medicines called carboxamides, barbiturates, succinimides, or oxazolidinediones.
• •Tell your provider if you have liver or kidney problems, porphyria (an enzyme problem), or high blood sugar.
• •Tell your provider if you drink alcohol. The label says alcohol can change phenytoin levels in the blood.
• •Tell your provider if you are pregnant, plan to become pregnant, or are breastfeeding.
• •Tell your provider about all medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements. The label says these can change phenytoin levels.
• •The label says to keep a list of your medicines and show it to your healthcare provider and pharmacist.

🔀 Phenytoin with other medicines, food and alcohol

The label says to discuss these with your doctor or pharmacist

• •The label says phenytoin is highly bound to blood proteins and is sensitive to interactions with other medicines.
• •Medicines that may raise phenytoin levels include some other seizure medicines (such as felbamate, oxcarbazepine, topiramate), some antifungals (such as fluconazole, ketoconazole), some antidepressants (such as fluoxetine, sertraline), some stomach acid reducers (such as cimetidine, omeprazole), some sulfonamide antibiotics, warfarin, and acute alcohol intake.
• •Medicines that may lower phenytoin levels include some antacids, some cancer medicines (such as cisplatin, methotrexate), some HIV medicines (such as ritonavir, nelfinavir), carbamazepine, vigabatrin, and chronic alcohol abuse.
• •The label says antacids may affect how phenytoin is absorbed, and phenytoin and antacids should not be taken at the same time of day.
• •The label says blood levels of phenytoin may be checked when a drug interaction is suspected, and doses may need to change when other medicines are started or stopped. This list is not complete.

Alcohol and food

The label says to tell your healthcare provider if you drink alcohol. It notes that acute alcohol intake may raise phenytoin levels, and chronic alcohol abuse may lower them. The label does not give specific food instructions beyond saying the tablet may be chewed or swallowed whole.

🤰 Phenytoin in pregnancy and breastfeeding

Pregnancy

The label says phenytoin may harm an unborn baby. Taking it during pregnancy may put the baby at risk for serious birth defects, and the baby may also have bleeding problems right after birth. If you become pregnant, the phenytoin level in your blood may drop, which may make seizures worse. The label says women of childbearing age should talk with their provider about other possible treatments, and that effective birth control should be used if pregnancy is not planned. The label also mentions the North American Antiepileptic Drug (NAAED) Pregnancy Registry, which you can join by calling 1-888-233-2334.

Breastfeeding

The label says phenytoin can pass into breast milk. You and your healthcare provider should decide together whether to take phenytoin while breastfeeding.

🗓️ Storage, missed doses and taking too much

Storage

The label says to store at 20 to 25 degrees C (68 to 77 degrees F) and to protect from moisture. Keep this medicine and all drugs out of the reach of children. The label notes that the unit dose package is not child resistant and is intended for institutional use only.

If a dose is missed

The label does not say.

If too much is taken

The label describes overdose symptoms that may include eye movement problems (nystagmus), loss of coordination (ataxia), slurred speech (dysarthria), tremor, lethargy, blurred vision, nausea, and vomiting. It also says a person may become comatose and have low blood pressure, and that slow heartbeat and cardiac arrest have been reported. The label notes that death is caused by breathing and circulation problems. If you think someone has taken too much phenytoin, this is a medical emergency, so seek emergency help right away.

🗒️ Questions to ask about Phenytoin

• Why am I being prescribed phenytoin instead of another seizure medicine?
• How will you check whether my phenytoin dose is working, and will I need blood level tests?
• What should I do if I miss a dose, and who should I call if I am unsure?
• Which of my current medicines, vitamins, or supplements could change my phenytoin levels?
• How much alcohol, if any, is safe for me to drink while taking phenytoin?
• What warning signs should prompt me to call you right away?
• If I become pregnant or plan to become pregnant, what should I do?

❓ Phenytoin: frequently asked questions