Foscarnet

Foscarnet is a prescription medication used to treat cytomegalovirus (CMV) retinitis in people with AIDS. It also treats the herpes simplex virus (HSV) in people with a weak immune system.

• Foscarnet is available under various brand names: Foscavir

Common side effects of Foscarnet include:

• fever, flu-like symptoms;
• nausea, vomiting, diarrhea;
• chest pain, back pain; or
• headache.

Serious side effects of Foscarnet include:

• hives; 
• difficult breathing; 
• swelling of the theeface, lips, tongue, or throat.
• pain or burning while urinating;
• a seizure (convulsions);
• headache with chest pain and severe dizziness, fainting, fast or pounding heartbeats;
• low white blood cell counts--fever, swollen gums, painful mouth sores, pain when swallowing, skin sores, cold or flu symptoms, cough, trouble breathing;
• low red blood cells (anemia)--pale skin, feeling light-headed or short of breath, rapid heart rate, trouble concentrating;
• low calcium--numbness or tingly feeling around your mouth, fast or slow heart rate, muscle tightness or contraction, overactive reflexes;
• low potassium--constipation, numbness or tingling, tiredness, muscle weakness, slow heart rate, fainting; or
• kidney problems--little or no urinating; painful or difficult urination; swelling in the feet or ankles; feeling tired or short of breath.

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 such as fast, irregular, or pounding heartbeats; fluttering in the chest; shortness of breath; sudden dizziness, lightheartedness, 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 Intravenous for 14-21 days; infuse Intravenous over at least 60 min  
• Maintenance: 90-120 mg/kg Intravenous once a day; infuse Intravenous over at least 60-90 min

Herpes Simplex

Adult dosage

• Option 1: 40 mg/kg every 8 hours Intravenous for 14-21 days; infuse Intravenous over at least 60 min  
• Option 2: 40-60 mg/kg Intravenous every 12 hours for 14-21 days; infuse Intravenous over at least 60 min

Dosage Considerations – Should be Given as Follows: 

• See “Dosages”

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 56 other drugs.
• Foscarnet has moderate interactions with at least 103 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 health care professional or doctor for additional medical advice, or if you have health questions or concerns.

Contraindications

• Hypersensitivity to Foscarnet
• kidney disease;
• heart disease, heart rhythm disorder;
• personal or family history of long QT syndrome;
• an electrolyte imbalance (such as low levels of calcium, potassium, or magnesium in your blood);
• epilepsy or other seizure disorder; or
• if you are on a low salt diet. 

Effects of drug abuse

• None

Short-Term Effects

• See “What Are Side Effects Associated with Using Foscarnet?”

Long-Term Effects

• See “What Are Side Effects Associated with Using Foscarnet?”

Cautions

• Foscarnet can harm your kidneys. This effect is increased when you also use certain other medicines, including antivirals, chemotherapy, injected antibiotics, medicine for bowel disorders, medicine to prevent organ transplant rejection, injectable osteoporosis medication, and some pain or arthritis medicines (including aspirin, Tylenol, Advil, and Aleve).
• Your kidney function and electrolytes (potassium, sodium, magnesium, phosphorus) will need to be tested often.
• Injecting foscarnet too fast can cause dangerous or unwanted side effects.
• Avoid getting this medicine in your eyes, as it may cause burning or irritation. If it does get into your eyes rinse with water and call your doctor.
• This medicine may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert.

Pregnancy and Lactation

• It is not known whether this Foscarnet will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant.
• Lactation
  • It is not known whether foscarnet passes into breast milk or if it could harm a nursing baby. You should not breastfeed while using this Foscarnet.