Fosphenytoin (Injection)


Fosphenytoin (fos-FEN-i-toin)

Treats certain types of seizures. This medicine is an anticonvulsant.

Brand Name(s)

Novaplus Fosphenytoin Sodium

There may be other brand names for this medicine.

When This Medicine Should Not Be Used

You should not receive this medicine if you have had an allergic reaction to fosphenytoin or to similar medicines (such as ethotoin, phenytoin, Dilantin®, or Peganone®). Do not use this medicine if you are pregnant or if you also take delavirdine (Rescriptor®). Do not use this medicine if you have certain heart rhythm problems.

How to Use This Medicine


  • Fosphenytoin is 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 your muscle or through a needle placed in one of your veins.

Drugs and Foods to Avoid

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

  • Make sure your doctor knows if you also use amiodarone (Cordarone®), aspirin, chloramphenicol (Chloromycetin®, Chloroptic®), chlordiazepoxide (Librium®), diazepam (Valium®), disulfiram (Antabuse®), fluorouracil, halothane (Fluothane®), isoniazid (Nydrazid®), methylphenidate (Ritalin®), or tolbutamide (Orinase®). Tell your doctor if you use other medicines to treat seizures (such as carbamazepine, ethosuximide, felbamate, oxcarbazepine, phenobarbital, quetiapine, sodium valproate, topiramate, valproic acid, Klonopin®, Tegretol®, Topamax®, or Zarontin®), medicine to treat fungal infections (such as fluconazole, itraconazole, ketoconazole, voriconazole, Nizoral®, Sporanox®, or Vfend®), medicine to treat depression (such as fluoxetine, fluvoxamine, paroxetine, sertraline, trazodone, Paxil®, or Prozac®), stomach medicines (such as cimetidine, ranitidine, omeprazole, Prilosec®, Tagamet®, or Zantac®), a phenothiazine medicine (such as prochlorperazine, Compazine®, Mellaril®, Phenergan®, Thorazine®, or Trilafon®), or a blood thinner (such as warfarin, Coumadin®).
  • Tell your doctor if you also use doxycycline (Vibramycin®), furosemide (Lasix®), irinotecan (Camptosar®), paclitaxel (Taxol®), quinidine (Cardioquin®), reserpine, rifampin (Rifadin®, Rimactane®), teniposide (Vumon®), theophylline (Theo-Dur®), Vitamin D, medicine to treat HIV infection (such as amprenavir, efavirenz, indinavir, lopinavir, nelfinavir, ritonavir, saquinavir, Fortovase®, Invirase®, Kaletra®, or Sustiva®), steroid medicine (such as dexamethasone, prednisolone, prednisone, or Medrol®), or birth control pills.
  • Do not drink alcohol while you are using this medicine.

Warnings While Using This Medicine

  • Using this medicine while you are pregnant can harm your unborn baby. Use an effective form of birth control to keep from getting pregnant. If you think you have become pregnant while using the medicine, tell your doctor right away. Your doctor may want you to join a pregnancy registry for patients who use a seizure medicine.
  • Make sure your doctor knows if you are breastfeeding or if you have kidney disease, liver disease, blood or bone marrow problems, heart failure, low blood pressure, lymph node problem (such as lymphadenopathy), an enzyme problem (such as porphyria), or diabetes.
  • Do not stop using this medicine suddenly without asking your doctor. You may need to slowly decrease your dose before stopping it completely. Your seizures may return or occur more often if you stop this medicine suddenly.
  • Stop using this medicine and check with your doctor right away if you develop a fever; rash; swollen, painful, or tender lymph glands in the neck, armpit, or groin; unusual bleeding or bruising; or yellow eyes or skin. These may be symptoms of a serious and life-threatening allergic reaction.
  • This medicine may cause purple glove syndrome. Tell your doctor right away if you have skin discoloration, pain, or swelling at or near the injection site after you receive this medicine. This reaction may occur days after you receive this medicine.
  • 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 raise or lower your blood sugar, or it may cover up symptoms of very low blood sugar (hypoglycemia).
  • Make sure any doctor or dentist who treats you knows that you are using this medicine. This medicine may affect the results of certain medical tests.
  • Birth control pills may not work while you are using this medicine. Use another form of birth control along with your birth control pills to avoid pregnancy.
  • Your doctor will need to check your progress at regular visits while you are using this medicine. Be sure to keep all appointments. Blood tests may also be needed to check for side effects.

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
  • Fast, slow, pounding, or uneven heartbeat
  • Fever, chills, cough, sore throat, and body aches
  • Lightheadedness, dizziness, or fainting
  • Loss of seizure control
  • Pain, skin discoloration, or swelling at or near the injection site
  • Severe burning, itching, or tingling feelings
  • Severe confusion, unsteadiness, trembling, or other problems with muscle control or coordination
  • Tender lymph glands in the neck, armpit, or groin
  • Uncontrolled eye movements
  • Unusual bleeding, bruising, tiredness, or weakness
  • Yellowing of the skin or the whites of your eyes

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

  • Headache
  • Mild skin rash or itching
  • Nausea or vomiting
  • Nervousness
  • Ringing in the ears
  • Sleepiness or unusual drowsiness

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 06/12/2013

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This page was last updated: September 18, 2013

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