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 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 is not a cure for CMV or HSV, and your virus may progress during or after treatment.
Foscarnet may also be used for other purposes not listed in this medication guide.
What is the most important information I should know about foscarnet?
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.
Foscarnet can be harmful to the kidneys, and these effects are increased when foscarnet is used together with other medicines that can harm the kidneys. Before using foscarnet, tell your doctor about all other medications you use. Many other drugs (including some over-the-counter medicines) can be harmful to the kidneys.
Foscarnet is not a cure for CMV or HSV, and your virus may progress during or after treatment.
What should I discuss with my health care provider before using foscarnet?
You should not use this medication if you are allergic to foscarnet.
If you have any of these other conditions, you may need a dose adjustment or special tests to safely use this medication:
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.
FDA pregnancy category C. It is not known whether foscarnet is harmful to an unborn baby. Before taking this medication, 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.