foscarnet

Foscarnet is a prescription medication used for the treatment of cytomegalovirus (CMV) eye infections (CMV retinitis) in patients with AIDS. It is also used to treat herpes simplex in patients with acyclovir resistance who are immunocompromised.

Contraindications

• Hypersensitivity

Effects of drug abuse

• None

Short-Term Effects

• See “What are the side effects of foscarnet?”

Long-Term Effects

• See “What are the side effects of foscarnet?”

Cautions

• Caution with renal impairment
• Do not administer by rapid or bolus IV injection; use infusion pump
• May be associated with changes in serum electrolytes changes including hypocalcemia, hypo- or hyperphosphatemia, hypomagnesemia, or hypokalemia
• Serious acute hypersensitivity reactions (e.g., anaphylactic shock, urticaria, angioedema) reported; if such acute reactions occur, discontinue therapy; and institute appropriate medical therapy immediately
• Cases of status epilepticus reported; several cases of seizures associated with death; electrolyte abnormalities may increase risk of seizures
• Associated with prolongation of QT interval, an ECG abnormality that has been associated with torsades de pointes, reported during postmarketing surveillance; has occurred with confounding risk factors such as underlying cardiac disease, electrolyte abnormalities and other concomitant medications; use caution in patients with history of QT prolongation, taking medications known to prolong the QT interval, patients with electrolyte disturbances, or patients who have other risk factors for QT prolongation; electrocardiograms (ECGs) and measurement of electrolytes should be obtained prior to treatment initiation and periodically during treatment
• Due to sodium content of foscarnet (240 micromoles (5.5 mg) of sodium per mL); avoid foscarnet use when IV infusion of large amount of sodium or water may not be tolerated (e.g. in patients with cardiomyopathy); avoid foscarnet use in patients on a controlled sodium diet

Common side effects of foscarnet include:

• fever,
• flu-like symptoms,
• nausea,
• vomiting,
• diarrhea,
• chest pain,
• back pain, and
• headache

Serious side effects of foscarnet include:

• hives,
• difficulty breathing,
• swelling of the face, lips, tongue, or throat,
• pain or burning when you urinate,
• seizures,
• headache with chest pain and severe dizziness,
• fainting,
• fast or pounding heartbeats,
• fever,
• swollen gums,
• painful mouth sores,
• pain when swallowing,
• skin sores,
• cold or flu symptoms,
• cough,
• trouble breathing,
• pale skin,
• lightheadedness,
• shortness of breath,
• rapid heart rate,
• trouble concentrating,
• numbness or tingly feeling around the mouth,
• slow heart rate,
• muscle tightness or contraction,
• overactive reflexes,
• constipation,
• numbness or tingling,
• tiredness,
• muscle weakness,
• little or no urination,
• painful or difficulty urinating,
• sores around the genitals,
• swelling in the feet or ankles, and
• tiredness

Rare side effects of foscarnet include:

• none

Seek medical care or call 911 at once if you have the following serious side effects:

• Severe headache, confusion, slurred speech, arm or leg weakness, trouble walking, loss of coordination, feeling unsteady, very stiff muscles, high fever, profuse sweating, or tremors;
• Serious eye symptoms such as sudden vision loss, blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights;
• Serious heart symptoms include fast, irregular, or pounding heartbeats; fluttering in the chest; shortness of breath; sudden dizziness, lightheadedness, or passing out.

This is not a complete list of side effects and other serious side effects or health problems that may occur because of the use of this drug.

Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.

Adult dosage

Injectable solution

• 2.4 g/100 mL

CMV Retinitis

Adult dosage

• Induction: 60 mg/kg every 8 hours IV x14-21 days; infuse IV over at least 60 min  
• Maintenance: 90-120 mg/kg IV every day; infuse IV over at least 60-90 min

Herpes Simplex

Adult dosage

• Option 1: 40 mg/kg IV every 8 hours  x14-21 days; infuse IV over at least 60 min  
• Option 2: 40-60 mg/kg IV every 12 hours x14-21 days; infuse IV over at least 60 min

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first

• Foscarnet has severe interactions with no other drugs.
• Foscarnet has serious interactions with at least 63 other drugs.
• Foscarnet has moderate interactions at least 105 other drugs.
• Foscarnet has minor interactions with at least 30 other drugs.

This information does not contain all possible interactions or adverse effects. Visit the RxList Drug Interaction Checker for any drug interactions. Therefore, before using this product, tell your doctor or pharmacist about all your products. 

Keep a list of all your medications with you and share this information with your doctor and pharmacist. Check with your healthcare professional or doctor for additional medical advice, or if you have health questions or concerns.

Pregnancy

• Use with caution if benefits outweigh risks during pregnancy

Breastfeeding

• It is not known if foscarnet is excreted in breast milk, so do not use while nursing.