Generic Name: Fosphenytoin (FOS fen i toyn)
Brand Name: Cerebyx
Medically reviewed on September 5, 2018
- This medicine may cause an abnormal heartbeat or low blood pressure if given too fast. Sometimes, this has been deadly. Your doctor will watch your heart closely when you get fosphenytoin. Tell your doctor right away if you have a fast, slow, or abnormal heartbeat during or after a dose.
Uses of Fosphenytoin:
- It is used to help control certain kinds of seizures.
What do I need to tell my doctor BEFORE I take Fosphenytoin?
- If you have an allergy to fosphenytoin, phenytoin, or any other part of fosphenytoin.
- If you are allergic to any drugs like this one, any other drugs, foods, or other substances. Tell your doctor about the allergy and what signs you had, like rash; hives; itching; shortness of breath; wheezing; cough; swelling of face, lips, tongue, or throat; or any other signs.
- If you have a slow heartbeat, heart block, or other heartbeat that is not normal.
- If you have had liver problems in the past while taking fosphenytoin or phenytoin.
- If you are taking delavirdine.
This is not a list of all drugs or health problems that interact with fosphenytoin.
Tell your doctor and pharmacist about all of your drugs (prescription or OTC, natural products, vitamins) and health problems. You must check to make sure that it is safe for you to take fosphenytoin with all of your drugs and health problems. Do not start, stop, or change the dose of any drug without checking with your doctor.
What are some things I need to know or do while I take Fosphenytoin?
- Avoid driving and doing other tasks or actions that call for you to be alert until you see how fosphenytoin affects you.
- This medicine interacts with many other drugs. The chance of fosphenytoin's side effects may be raised or how well fosphenytoin works may be lowered. The chance of the other drugs' side effects may also be raised. This may include very bad, life-threatening, or deadly side effects. Check with your doctor and pharmacist to make sure that it is safe for you to take fosphenytoin with all of your other drugs (prescription or OTC, natural products, vitamins).
- Do not stop taking fosphenytoin all of a sudden without calling your doctor. You may have a greater risk of seizures. If you need to stop this drug, you will want to slowly stop it as ordered by your doctor.
- Have the level of phenytoin in your blood checked as you have been told by your doctor. If the level is too high, some side effects may happen. This includes a type of brain problem that may not go back to normal. Talk with your doctor.
- If you have high blood sugar (diabetes), you will need to watch your blood sugar closely. Tell your doctor if you get signs of high blood sugar like confusion, feeling sleepy, more thirst, more hungry, passing urine more often, flushing, fast breathing, or breath that smells like fruit.
- Lymph node problems like cancer have happened in people taking fosphenytoin. It is not known if fosphenytoin may be the cause. Talk with your doctor if you have swollen glands.
- Very bad and sometimes deadly skin reactions (Stevens-Johnson syndrome/toxic epidermal necrolysis) have happened with fosphenytoin. People of Asian descent are most likely to get these. Get medical help right away if you have signs like red, swollen, blistered, or peeling skin (with or without fever); red or irritated eyes; or sores in your mouth, throat, nose, or eyes.
- This medicine may cause weak bones. This may happen more often if used for a long time. This may raise the chance of broken bones. Call your doctor right away if you have bone pain.
- This medicine may cause very bad and sometimes deadly heartbeats that are not normal. Call your doctor right away if you have a heartbeat that does not feel normal.
- If you are 65 or older, use fosphenytoin with care. You could have more side effects.
- Birth control pills and other hormone-based birth control may not work as well to prevent pregnancy. Use some other kind of birth control also like a condom when taking fosphenytoin.
- This medicine may cause harm to the unborn baby if you take it while you are pregnant. If you are pregnant or you get pregnant while taking fosphenytoin, call your doctor right away.
- A bleeding problem that can be life-threatening may happen in newborns if you took fosphenytoin during pregnancy. Talk with your doctor.
- Tell your doctor if you are breast-feeding. You will need to talk about any risks to your baby.
How is this medicine (Fosphenytoin) best taken?
Use fosphenytoin as ordered by your doctor. Read all information given to you. Follow all instructions closely.
- It is given as an infusion into a vein over a period of time.
- It may be given as a shot into a muscle.
- Tell all of your health care providers that you take fosphenytoin. This includes your doctors, nurses, pharmacists, and dentists.
- Talk with your doctor before you drink alcohol or use other drugs and natural products that slow your actions.
- Wear disease medical alert ID (identification).
- Follow laws about driving with a seizure problem.
- Take good care of your teeth. See a dentist often.
- Have blood work checked as you have been told by the doctor. Talk with the doctor.
- This medicine may affect certain lab tests. Tell all of your health care providers and lab workers that you take fosphenytoin.
What do I do if I miss a dose?
- Call your doctor to find out what to do.
See also: Dosage Information (in more detail)
What are some side effects that I need to call my doctor about right away?
WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:
- Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing, swallowing, or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
- Signs of low mood (depression), thoughts of killing yourself, nervousness, emotional ups and downs, thinking that is not normal, anxiety, or lack of interest in life.
- Signs of low potassium levels like muscle pain or weakness, muscle cramps, or a heartbeat that does not feel normal.
- Very bad dizziness or passing out.
- Trouble controlling body movements, twitching, change in balance, trouble swallowing or speaking.
- Feeling confused.
- Ringing in ears.
- Hearing loss.
- Swollen or sore gums.
- Not able to control eye movements.
- If seizures are worse or not the same after starting fosphenytoin.
- Irritation or swelling where the shot was given.
- Change in color of skin where drug is used.
- A burning, numbness, or tingling feeling that is not normal.
- A very bad and sometimes deadly effect has happened in people taking drugs for seizures like fosphenytoin. Call your doctor right away if you have swollen glands; fever; rash; chest pain; unable to pass urine or change in the amount of urine passed; or signs of liver problems like dark urine, feeling tired, not hungry, upset stomach or stomach pain, light-colored stools, throwing up, or yellow skin or eyes.
- Rarely, certain blood problems have happened with fosphenytoin. This can lead to bleeding problems or infections. Sometimes, these have been deadly. Tell your doctor right away if you have signs of infection like fever, chills, very bad sore throat, ear or sinus pain, cough, more sputum or change in color of sputum, pain with passing urine, mouth sores, or a wound that will not heal. Tell your doctor right away if you have any unexplained bruising or bleeding, or if you feel very tired or weak.
What are some other side effects of Fosphenytoin?
All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:
- Feeling sleepy.
- Dry mouth.
- Upset stomach or throwing up.
These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.
You may report side effects to the FDA at 1-800-FDA-1088. You may also report side effects at http://www.fda.gov/medwatch.
See also: Side effects (in more detail)
If OVERDOSE is suspected:
If you think there has been an overdose, call your poison control center or get medical care right away. Be ready to tell or show what was taken, how much, and when it happened.
How do I store and/or throw out Fosphenytoin?
- If you need to store fosphenytoin at home, talk with your doctor, nurse, or pharmacist about how to store it.
Consumer information use
- If your symptoms or health problems do not get better or if they become worse, call your doctor.
- Do not share your drugs with others and do not take anyone else's drugs.
- Keep a list of all your drugs (prescription, natural products, vitamins, OTC) with you. Give this list to your doctor.
- Talk with the doctor before starting any new drug, including prescription or OTC, natural products, or vitamins.
- Keep all drugs in a safe place. Keep all drugs out of the reach of children and pets.
- Throw away unused or expired drugs. Do not flush down a toilet or pour down a drain unless you are told to do so. Check with your pharmacist if you have questions about the best way to throw out drugs. There may be drug take-back programs in your area.
- Some drugs may have another patient information leaflet. Check with your pharmacist. If you have any questions about fosphenytoin, please talk with your doctor, nurse, pharmacist, or other health care provider.
- If you think there has been an overdose, call your poison control center or get medical care right away. Be ready to tell or show what was taken, how much, and when it happened.
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
More about fosphenytoin
- Fosphenytoin Side Effects
- During Pregnancy
- Dosage Information
- Drug Interactions
- Pricing & Coupons
- En Español
- Drug class: hydantoin anticonvulsants
Other brands: Cerebyx