Foscarnet

Foscarnet is a prescription medication used to treat cytomegalovirus (CMV) infections of the eye. Foscarnet is also used to treat herpes simplex virus (HSV) that is resistant to the antiviral acyclovir.

Foscarnet belongs to a group of drugs called antivirals. It works by preventing the spread of CMV disease or slowing the growth of CMV.

This medication is available in an injectable form to be given directly into a vein (IV) by a healthcare professional.

Common side effects of foscarnet include fever, nausea, anemia, and diarrhea.

Foscarnet is a prescription medication used to treat cytomegalovirus (CMV) eye infections in patients whose immune system is not working properly such as patients who have acquired immunodeficiency syndrome (AIDS) or who have received an organ transplant.

Foscarnet is also used to treat herpes simplex virus (HSV) of the mucous membranes that is resistant to the antiviral acyclovir in patients whose immune system is not working properly such as patients who have acquired immunodeficiency syndrome (AIDS) or who have received an organ transplant.

This medication may be prescribed for other uses. Ask your doctor or pharmacist for more information.

Foscarnet may be found in some form under the following brand names:

• Foscavir

Serious side effects have been reported with foscarnet. See the “Foscarnet Precautions” section.

Common side effects of foscarnet include the following:

• fever
• nausea
• vomiting
• anemia
• diarrhea
• decreased kidney function
• headache
• seizures

This is not a complete list of foscarnet side effects. Ask your doctor or pharmacist for more information.

Tell your doctor if you have any side effect that bothers you or that does not go away.

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

Tell your doctor about all the medicines you take, including prescription ad non-prescription medicines, vitamins, and herbal supplements. Especially tell your doctor if you take:

• pentamidine (Pentacrinat, NebuPent)
• medications that reduce drug clearance through the kidneys such as acyclovir (Zovirax), cidofovir (Vistide), ganciclovir (Cytovene), valacyclovir (Valtrex), valganciclovir (Valcyte), amphotericin B (Ambisome)
• ritonavir (Norvir), saquinavir (fortovase)
• medications that can damage the kidneys such as aminoglycosides. For example, gentamicin (Garamycin)

This is not a complete list of foscarnet drug interactions. Ask your doctor or pharmacist for more information.

Serious side effects have been reported with foscarnet including the following:

• a decline in kidney function. Toxicity from foscarnet may occur with kidney dysfunction. Your doctor may want to monitor your kidney functions with certain blood tests as well. Tell your healthcare provider right away right away if you have any of the following symptoms of kidney dysfunction:
  • swelling of face, ankles, hands, or feet
  • fatigue
  • paleness of skin
  • decreased urination
  • shortness of breath
  • change in blood pressures
• mineral and electrolyte abnormalities. Your doctor may monitor the levels of certain electrolytes in your blood while using this medication. Tell your doctor if you experience numbness in the extremities, dizziness, or seizures.
• seizures. If seizure or any of the above side effects should occur during the infusion, the dose may need to be adjusted or the medication may need to be stopped entirely.
• low red blood cell count (anemia). Tell your doctor if you have any of the following signs of anemia during treatment with foscarnet: feeling weak tired, or tiring easily, you look pale, you feel short of breath.
• low white blood cell count (neutropenia). A low white blood cell count can cause you to get infections, which may be serious. Serious illness or death can happen if it is not treated right away when white blood cell counts are very low. Tell your doctor right away if you have any of the following signs or symptoms of an infection: fever, shortness of breath, pain or burning on urination, chills, or cough. 
• nerve damage (neuropathy). This drug can cause nerve damage that can cause you to have tingling, burning, or painful sensations in your extremities. Tell your doctor right away if you experience pain or numbness in your hands or feet.
• changes in vision. Tell your healthcare provider right away if you experience any changes in vision.
• anxiety. Tell your healthcare provider right away if you feel more nervous, anxious, or notice any changes in mood.
• depression. Tell your healthcare provider right away if you notice any changes in mood.
• confusion. Tell your doctor right away if you feel more confused or notice any changes in mood.
• rash.
• increased sweating.

Do not take foscarnet if you are allergic to foscarnet or to any of its ingredients.

Medications can interact with certain foods. In some cases, this may be harmful and your doctor may advise you to avoid certain foods. In the case of foscarnet, there are no specific foods that you must exclude from your diet when receiving this medication.

Before taking foscarnet, tell your doctor about all of your medical conditions. Especially tell your doctor if you:

• are allergic to foscarnet or to any of its ingredients
• have or have had kidney problems

• have or have had anemia
• are pregnant or breastfeeding, or plan to become pregnant
• have or have had electrolyte problems in the past

Tell your doctor about all the medicines you take including prescription and non-prescription medicines, vitamins, and herbal supplements.

Tell your doctor if you are pregnant or plan to become pregnant.

The FDA categorizes medications based on safety for use during pregnancy. Five categories - A, B, C, D, and X, are used to classify the possible risks to an unborn baby when a medication is taken during pregnancy.

Foscarnet falls into category C. There are no well-controlled studies that have been done in pregnant women. Foscarnet should be used during pregnancy only if the possible benefit outweighs the possible risk to the unborn baby.

Tell your doctor if you are breastfeeding or plan to breastfeed.

It is not known if foscarnet crosses into human milk. Because many medications can cross into human milk and because of the possibility for serious adverse reactions in nursing infants with use of this medication, a choice should be made whether to stop nursing or stop the use of this medication. Your doctor and you will decide if the benefits outweigh the risk of using foscarnet.

Foscarnet comes in an injectable form and is given directly into a vein (IV) via a controlled infusion by a healthcare professional every 8-12 hours.

Your doctor will likely hydrate you with IV fluids while you are being treated with foscarnet.

The foscarnet dose you receive is based on your weight, whether the infection you have is resistant to certain other medications, and your kidney function. A healthcare professional will calculate your dose based on these factors. It will be given every 8 or 12 hours for 2 or 3 weeks, or until you are healed.

If foscarnet is administered by a healthcare provider in a medical setting, it is unlikely that an overdose will occur. However, if overdose is suspected, seek emergency medical attention.

Keep all your appointments with your doctor and laboratory. Your doctor will likely order blood tests to check your kidney function while you are being treated.

WARNING

RENAL IMPAIRMENT IS THE MAJOR TOXICITY OF FOSCARNET SODIUM INJECTION. FREQUENT MONITORING OF SERUM CREATININE, WITH DOSE ADJUSTMENT FOR CHANGES IN RENAL FUNCTION, AND ADEQUATE HYDRATION WITH ADMINISTRATION OF FOSCARNET SODIUM INJECTION, IS IMPERATIVE.

SEIZURES, RELATED TO ALTERATIONS IN PLASMA MINERALS AND ELECTROLYTES, HAVE BEEN ASSOCIATED WITH FOSCARNET SODIUM INJECTION TREATMENT. THEREFORE, PATIENTS MUST BE CAREFULLY MONITORED FOR SUCH CHANGES AND THEIR POTENTIAL SEQUELAE. MINERAL AND ELECTROLYTE SUPPLEMENTATION MAY BE REQUIRED.

FOSCARNET SODIUM INJECTION IS INDICATED FOR USE ONLY IN IMMUNOCOMPROMISED PATIENTS WITH CMV RETINITIS AND MUCOCUTANEOUS ACYCLOVIR-RESISTANT HSV INFECTIONS.