What is foscarnet?

Foscarnet is  an antiviral medication  that prevents certain virus cells from multiplying  in your body. 

Foscarnet is used to treat cytomegalovirus (CMV) retinitis in people with AIDS. Foscarnet is not a cure for CMV, and the virus may progress during  or after treatment. 

Foscarnet  is also used to treat herpes simplex virus (HSV) in people with a weak immune system. Foscarnet is usually given  for HSV after  other antiviral medications have been tried without successful treatment. 

Foscarnet  may also be used for purposes other than those listed in this medication guide. 

What are  the possible  side effects of foscarnet? 

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of  your face, lips, tongue, or throat. 

Stop  using foscarnet  and call  your doctor at once if you have any  of these serious side effects: 

• urinating less than usual or not at all; 
• dry mouth, increased thirst, drowsiness, restless feeling, confusion, nausea, vomiting, increased urination, muscle pain or weakness, fast heart rate, feeling light-headed, fainting, or seizure (convulsions); 
• fever, chills, body aches, flu symptoms; 
• pale skin, easy bruising or bleeding; 
• numbness or tingling around your mouth or in your hands or feet; 
• restless muscle movements in your eyes, tongue, jaw, or neck; 
• trouble breathing; or 
• pain or burning when  you urinate. 
• Keep using  foscarnet and talk with your doctor if you have any  of these less serious side effects: 
• anxiety, confusion, depressed mood; 
• nausea, stomach pain, vomiting; 
• headache, dizziness; 
• cough; 
• increased sweating; 
• skin rash; 
• problems with vision; 
• weakness, tired feeling; 
• joint or muscle pain; or 
• pain or swelling where  the injection was given. 

Side effects other than those listed here may also occur. Talk  to your doctor about any side effect that seems unusual or that is especially bothersome. You may report side effects  to FDA 

What is the most important information I should know about foscarnet? 

Foscarnet is not a cure for CMV, and the virus may progress during or after treatment. 

Before using foscarnet, tell  your doctor if you have kidney disease, a seizure disorder, heart disease, a nerve disorder, or an electrolyte imbalance such  as low calcium, potassium, or magnesium. 

To be  sure this medication is not causing harmful effects, your blood will need to be tested on a regular basis. Your kidney function may also need to be tested, and  you may also  need regular eye exams. Do not miss any scheduled visits  to your doctor. 

Stop using foscarnet and call  your doctor at once if you urinate less than usual or not at all, or if you have numbness or tingling around your mouth, uncontrolled muscle movements, or pain or burning  when you urinate. 

There  are many other medicines that can cause kidney damage or lower calcium levels  and should not be used together with foscarnet. Tell your doctor about  all the prescription and over-the-counter  medications you use. This includes vitamins, minerals, herbal products,  and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor. Keep a list with you  of all the medicines you use and show this list to any doctor or other healthcare provider who treats you. 

What should I discuss with my  health care provider before using foscarnet? 

Do not use this medication if you are allergic to foscarnet. 

Before using foscarnet,  tell your doctor if  you are allergic  to any drugs, or if you have: 

• kidney disease; 
• epilepsy or other seizure disorder; 
• a history of head injury  or brain tumor; 
• heart disease; 
• a nerve disorder; 
• low levels  of calcium, magnesium, or potassium in your blood; or 
• any other type of electrolyte imbalance. 

If you have any of these conditions, you may not be able to use foscarnet,  or you may need dosage adjustments or special tests during treatment. 

FDA pregnancy category C. This medication may be harmful  to an unborn baby. Tell  your doctor if  you are pregnant or plan to become pregnant during treatment. 

It is not known whether foscarnet passes into breast milk or if it could harm a nursing baby. Do not use this medication without telling  your doctor if you are breast-feeding a baby. 

How is foscarnet given? 

Foscarnet is given as an injection through a needle placed into a vein. The medicine must be given slowly through an IV infusion pump, and can take up to 2 hours to complete. 

You may be given instructions on how to inject your medicine at home. Do not use this medicine at home if you do not fully understand how to give the injection and properly dispose of needles and other items used in giving the medicine. 

With each foscarnet injection, you may be given IV fluids to keep you from getting dehydrated. 

Foscarnet is usually given for 2 to 3 weeks. Your doctor may occasionally change your dose to make sure you get the best results from this medication. 

You may need to mix foscarnet with a liquid (diluent) before using it. If you are using the injections at home, be sure you understand how to properly mix and store the medication. 

Foscarnet should be clear and colorless. Do not use the medication if it has changed colors or has any particles in it. Call your doctor for a new prescription. 

To be sure this medication is not causing harmful effects, your blood will need to be tested on a regular basis. Your kidney function may also need to be tested, and you may also need regular eye exams. Do not miss any scheduled visits to your doctor. 

Store foscarnet at room temperature away from very hot or very cold temperature. 

Notes: Dr. Nelson Crumfield

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EditText of this page (last edited June 10, 2010)