Fosphenytoin (Injection)


Fosphenytoin (fos-FEN-i-toin)

Treats seizures. This medicine is an anticonvulsant.

Brand Name(s)

Cerebyx, Novaplus Fosphenytoin Sodium

When This Medicine Should Not Be Used

How to Use This Medicine


  • This medicine is usually given only for a short time when you cannot take other forms of anticonvulsant medicine, such as when you are in the hospital or when you have surgery.
  • A nurse or other trained health professional will give you this medicine in a hospital. This medicine is given as a shot into a muscle or into a vein.
  • After your condition improves, your doctor might switch you to an oral medicine that works the same way. Talk to your doctor if you have any concerns about this.

Drugs and Foods to Avoid

Ask your doctor or pharmacist before using any other medicine, including over-the-counter medicines, vitamins, and herbal products.

  • There are many other drugs that can interact with phenytoin. Make sure your doctor knows about all other medicines you are using.
  • Make sure your doctor knows if you are using other medicine for seizures, such as carbamazepine, ethosuximide, felbamate, methsuximide, oxcarbazepine, phenobarbital, quetiapine, valproate, topiramate, valproic acid, Depakene®, Tegretol®, Zarontin®).
  • Make sure your doctor knows if you also use St John's wort, amiodarone (Cordarone®), quinidine (Quinaglute®), aspirin, chlordiazepoxide (Librium®), cyclosporine (Gengraf®, Neoral®, Sandimmune®), diazepam (Valium®), digoxin (Lanoxin®), disulfiram (Antabuse®), folic acid, furosemide (Lasix®), isoniazid (Nydrazid®), methylphenidate (Ritalin®), nisoldipine (Sular®), praziquantel (Biltricide®), reserpine, sucralfate (Carafate®), theophylline (Theo-Dur®), tolbutamide (Orinase®), vitamin D, medicine to lower cholesterol (such as atorvastatin, fluvastatin, simvastatin), medicine to treat depression (such as fluoxetine, fluvoxamine, paroxetine, sertraline, trazodone), a phenothiazine medicine (such as promethazine, Phenergan®, Thorazine®), or a blood thinner (such as warfarin, Coumadin®, Jantoven®).
  • Make sure your doctor knows if you also use cancer medicine (such as bleomycin, capecitabine, carboplatin, cisplatin, doxorubicin, fluorouracil, irinotecan, methotrexate, paclitaxel, teniposide, Camptosar®, Taxol®, Trexall®), medicine to treat an infection (such as chloramphenicol, doxycycline, fluconazole, itraconazole, ketoconazole, rifampin, voriconazole, Nizoral®), a sulfa drug (such as sulfamethoxazole/trimethoprim, sulfasalazine, Azulfidine®, Bactrim®, Septra®), a steroid medicine (such as hydrocortisone, methylprednisolone, prednisolone, prednisone), or medicine to treat HIV/AIDS (such as amprenavir, efavirenz, fosamprenavir, indinavir, lopinavir, nelfinavir, ritonavir, saquinavir, Kaletra®, Norvir®).
  • Birth control pills may not work as well while you are using this medicine. Use another form of birth control along with your pills to avoid pregnancy.
  • Do not drink alcohol while you are using this medicine.

Warnings While Using This Medicine

  • It is not safe to take this medicine during pregnancy. It could harm an unborn baby. Tell your doctor right away if you become pregnant.
  • Make sure your doctor knows if you are breastfeeding, or if you have kidney disease, liver disease, heart failure, low blood pressure, or porphyria.
  • Tell your caregiver right away if your heartbeat becomes faster, slower, or pounding or if you feel lightheaded or faint while you are receiving this medicine. You might be getting the medicine too fast, and your caregiver will slow down the rate.
  • Serious skin reactions can occur with this medicine. Check with your doctor right away if you have blisters, peeling skin, redness, skin rash, sores, fever, or chills.
  • Tell your doctor right away if you develop a fever, rash, and swollen or tender glands. Other symptoms might be unusual bleeding or bruising, or yellow eyes or skin. These may be symptoms of a serious and life-threatening reaction to this medicine.
  • Tell your doctor right away if you have skin color changes, pain, or swelling where the needle is placed. This could occur days after you receive this medicine, but it is still important that you call right away. This problems is sometimes called "purple glove syndrome."
  • Do not stop using this medicine suddenly. Your doctor will need to slowly decrease your dose before you stop it completely.
  • This medicine may make you dizzy or drowsy. Do not drive, use machines, or do anything that could be dangerous until you know how this medicine affects you.
  • This medicine may affect blood sugar levels. If you have diabetes and you notice a change in your blood sugar levels or if you have any questions, check with your doctor.
  • Tell any doctor or dentist who treats you that you are using this medicine. This medicine may affect certain medical test results.
  • Your doctor will do lab tests at regular visits to check on the effects of this medicine. Keep all appointments.

Possible Side Effects While Using This Medicine

Call your doctor right away if you notice any of these side effects:

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Blistering, peeling, or red skin rash
  • Dark-colored urine or pale stools, nausea, vomiting, loss of appetite, pain in your upper stomach, yellow skin or eyes
  • Fast, slow, or pounding heartbeat, lightheadedness or fainting
  • Feeling depressed, irritable, or restless
  • Fever, chills, cough, sore throat, and body aches
  • Pain, changes in skin color, or swelling at or near the injection site
  • Severe confusion, problems with balance or walking, slurred speech, tremors
  • Swollen glands in your armpits, neck, or groin
  • Unusual bleeding, bruising, or weakness

If you notice these less serious side effects, talk with your doctor:

  • Mild confusion, slurred speech, clumsiness, problems with balance
  • Mild skin rash

If you notice other side effects that you think are caused by this medicine, tell your doctor

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088

Version Info

  • Last reviewed on 8/4/2014

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