Fosphenytoin

Fosphenytoin is an anticonvulsant used to prevent or control seizures. Fosphenytoin is used for a short time or when other forms of phenytoin cannot be given.

Fosphenytoin may also be used for reasons not mentioned in this medication guide.

Use only as directed. Inform your doctor if you are taking other medicines or have other medical conditions or allergies.

You should not use fosphenytoin if you are allergic to fosphenytoin or phenytoin, or if you have:

• slow heartbeats;
• Adams-Stokes syndrome (a heart rhythm disorder);
• heart block, AV block;
• liver problems after taking phenytoin (Dilantin); or
• if you also take delavirdine.

Tell your doctor if you have ever had:

• heart disease;
• liver or kidney disease;
• diabetes (fosphenytoin can raise your blood sugar);
• low blood pressure;
• porphyria (a genetic enzyme disorder that causes symptoms affecting the skin or nervous system); or
• if you drink large amounts of alcohol.

Patients of Asian ancestry may have a higher risk of developing a rare but serious skin reaction to fosphenytoin. You may need a blood test to determine your risk of this skin reaction.

Do not start or stop seizure medication during pregnancy without your doctor's advice. Fosphenytoin may harm an unborn baby, but having a seizure during pregnancy could harm both mother and baby. Preventing seizures may outweigh these risks. Tell your doctor right away if you become pregnant.

There may be other seizure medications that are safer to use during pregnancy.

If you receive fosphenytoin during pregnancy, be sure to tell the doctor who delivers your baby. Both you and the baby may need medication to prevent bleeding during delivery and just after birth.

Fosphenytoin can make birth control pills less effective. Ask your doctor about other birth control options such as an injection, implant, skin patch, vaginal ring, condom, diaphragm, cervical cap, or contraceptive sponge.

Ask a doctor if it is safe to breastfeed while using this medicine.

Stop using fosphenytoin and get emergency medical help if you notice any signs of an allergic reaction, such as hives, trouble breathing, or swelling in your face or throat, or if you have a severe skin reaction, which can include fever, sore throat, burning eyes, skin pain, and a red or purple skin rash that blisters and peels.

Seek medical treatment if you experience a serious drug reaction that could affect multiple parts of your body. Symptoms may include: skin rash, fever, swollen glands, muscle aches, severe weakness, unusual bruising, or yellowing of your skin or eyes.

Fosphenytoin may cause serious side effects. Call your doctor immediately if you experience:

• very slow heartbeats or shortness of breath;
• feeling light-headed, as if you might pass out;
• confusion or unusual thoughts or behavior;
• pain, swelling, and purple discoloration at the injection site (which may spread to your hand or fingers);
• tingling or burning sensations;
• sudden fever, chills, sore throat, or weakness;
• easy bruising or unusual bleeding;
• signs of swollen lymph nodes, including a painful, warm, or red lump under your skin, unusual tiredness, skin rash, unexplained weight loss, fever, or night sweats; or
• low blood potassium, which may cause leg cramps, constipation, irregular heartbeats, fluttering in your chest, increased thirst or urination, numbness or tingling, or muscle weakness or a limp feeling.

Common side effects of fosphenytoin may include:

• dizziness or drowsiness;
• unusual or involuntary eye movements;
• vomiting;
• itching; or
• problems with balance or muscle movement.

This is not a complete list of side effects, and others may occur. Call your doctor for medical advice about side effects. You can report side effects to the FDA at 1-800-FDA-1088.

Fosphenytoin is injected into a muscle or a vein by a healthcare provider.

You will be watched closely for 10 to 20 minutes to make sure this medicine does not cause harmful effects.

Your breathing, blood pressure, heart rhythm, oxygen levels, and other vital signs will be watched closely.

This medicine can affect the results of certain medical tests. Tell any doctor who treats you that you are using fosphenytoin.

Seizures may increase if you stop using fosphenytoin suddenly.. Ask your doctor before stopping the medicine.

Call your doctor for instructions if you miss a dose of Fosphenytoin.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222. An overdose can be fatal.

Overdose symptoms may include weakness, nausea, vomiting, feeling light-headed, fast or slow heart rate, tingling, muscle spasms, seizures, or slow breathing (breathing may stop).

Avoid drinking alcohol.

Sometimes it is not safe to use certain medications together. Some drugs can change how much of another drug is in your blood, which may increase side effects or make the medications less effective.

Using fosphenytoin with other drugs that cause drowsiness can make this effect worse. Ask your doctor before using opioid medication, a sleeping pill, a muscle relaxer, or medicine for anxiety or seizures.

Many drugs can affect fosphenytoin. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed here. Tell your doctor about all other medicines you are using.