Precautions

Drug information provided by: Merative, Micromedex®

It is very important that your doctor check your progress closely while you are receiving this medicine. This is to see if the medicine is working properly and to allow for a change in the dose. Blood tests may be needed to check for any unwanted effects.

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 taking a seizure medicine.

Do not receive this medicine while you are also taking delavirdine (Rescriptor®). Using these medicines together may cause delavirdine to not work as well for you.

This medicine may increase your risk for heart or blood vessel problems. Check with your doctor right away if you have blurred vision, chest pain, confusion, lightheadedness, dizziness, or fainting, fast or irregular heartbeat, trouble breathing, or unusual tiredness or weakness.

This medicine may cause some people to become dizzy, lightheaded, faint, or less alert than they are normally. Make sure you know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are dizzy or are not alert and able to see well.

Do not stop using this medicine without first checking with your doctor. Stopping the medicine suddenly may cause your seizures to return or to occur more often.

Serious skin reactions (eg, toxic epidermal necrolysis, Stevens-Johnson syndrome, acute-generalized exanthematous pustulosis) can occur with this medicine. Check with your doctor right away if you or your child have blistering, peeling, or loose skin, chills, cough, diarrhea, itching, joint or muscle pain, red irritated eyes, red skin lesions, often with a purple center, sore throat, sores, ulcers, or white spots in the mouth or on the lips, or unusual tiredness or weakness while you are using this medicine.

Tell your doctor right away if you or your child develop a black, tarry stools, chest pain, chills, cough, fever, rash, swollen, painful, or tender lymph glands in the neck, armpit, or groin, painful or difficult urination, sore throat, sores, ulcers, or white spots on the lips or in the mouth, unusual bleeding or bruising, or yellow eyes or skin after using this medicine. These may be symptoms of a serious and life-threatening condition called drug reaction with eosinophilia and systemic symptoms (DRESS).

This medicine may cause serious allergic reactions, including angioedema. These can be life-threatening and require immediate medical attention. Tell your doctor right away if you or your child have a rash, itching, hoarseness, trouble breathing, trouble swallowing, or any swelling of your hands, face, or mouth after using this medicine.

This medicine may cause liver problems. Check with your doctor right away if you or your child have a dark-colored urine, general feeling of tiredness or weakness, headache, light-colored stools, stomach pain continuing, vomiting, or yellow eyes or skin.

Fosphenytoin can temporarily lower the number of white blood cells in your blood, increasing the chance of getting an infection. It can also lower the number of platelets, which are necessary for proper blood clotting. If this occurs, there are certain precautions you can take, especially when your blood count is low, to reduce the risk of infection or bleeding:

  • If you can, avoid people with infections. Check with your doctor immediately if you think you are getting an infection or if you get a fever or chills, cough or hoarseness, lower back or side pain, or painful or difficult urination.
  • Check with your doctor immediately if you notice any unusual bleeding or bruising, black, tarry stools, blood in the urine or stools, or pinpoint red spots on your skin.
  • Be careful when using a regular toothbrush, dental floss, or toothpick. Your medical doctor, dentist, or nurse may recommend other ways to clean your teeth and gums. Check with your medical doctor before having any dental work done.
  • Do not touch your eyes or the inside of your nose unless you have just washed your hands and have not touched anything else in the meantime.
  • Be careful not to cut yourself when you are using sharp objects such as a safety razor or fingernail or toenail cutters.
  • Avoid contact sports or other situations where bruising or injury could occur.

Tell your doctor right away if your skin feels like it is burning, crawling, or itching, or if you have numbness, prickling, "pins and needles", or tingling feelings after receiving fosphenytoin injection.

This medicine may cause purple glove syndrome. Tell your doctor right away if you have skin discoloration, pain, or swelling at the injection site after receiving this medicine.

This medicine may affect blood sugar levels. If you notice a change in the results of your blood or urine sugar tests or if you have any questions, check with your doctor.

Birth control pills may not work while you are using this medicine. To keep from getting pregnant, use another form of birth control along with your birth control pills. Other forms include a condom, a diaphragm, or a contraceptive foam or jelly.

Avoid drinking alcohol while you are receiving this medicine.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

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Portions of this document last updated: April 01, 2024

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