Generic Name: foscarnet
Brand and Other Names: Foscavir, Phosphonoformic acid
Drug Class: Antivirals, CMV; Antivirals, Other
What is foscarnet, and what is it used for?
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.
Warnings
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
What are the side effects of foscarnet?
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.

QUESTION
What is HIV? See AnswerWhat are dosages of foscarnet?
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
What other drugs interact with foscarnet?
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 and breastfeeding
- Use with caution if benefits outweigh risks during pregnancy
- It is not known if foscarnet is excreted in breast milk, so do not use while nursing.
Summary
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. Common side effects of foscarnet include fever, flu-like symptoms, nausea, vomiting, diarrhea, chest pain, back pain, and headache. Do not take if you have drug hypersensitivity or are breastfeeding. Use with caution if you have renal impairment.
Multimedia: Slideshows, Images & Quizzes
-
Cold Sores Causes, Remedies, & Diagnosis
How do you get rid of cold sores? First learn about the herpes virus and how it causes cold sores. When are cold sores...
-
What Are HIV & AIDS? Symptoms, Treatment, and Prevention
HIV, or human immunodeficiency virus, causes acquired immunodeficiency syndrome, or AIDS. Learn about HIV symptoms, HIV test, HIV...
-
HIV AIDS: Myths and Facts
What is HIV versus AIDS? What are the symptoms of HIV? Is there an HIV cure? Discover myths and facts about living with HIV/AIDS....
-
A Timeline of the HIV/AIDS Pandemic
Get a historical overview of the HIV/AIDS pandemic from human contraction to the present through this slideshow of pictures.
-
Picture of HIV Lipodystrophy
HIV lipodystrophy describes a constellation of changes in subcutaneous and visceral fat distribution in patients on...
-
HIV & AIDS Quiz: HIV Testing & Symptoms
Now, more than ever, you should know about HIV/AIDS, especially its causes, symptoms treatments, and complications. Take the...
-
Picture of Herpes Simplex Virus Type 1
A herpes virus that causes cold sores and fever blisters in and around the mouth. See a picture of Herpes Simplex Virus Type 1...
-
Picture of Herpes Simplex Virus Type 2
A herpes virus that causes genital herpes, which is characterized by sores in the genital area. See a picture of Herpes Simplex...
-
Picture of HIV/AIDS
Acronym for the Human Immunodeficiency Virus, the cause of AIDS (acquired immunodeficiency syndrome). See a picture of HIV/AIDS...
-
Picture of Herpes Blister (Cold Sore)
Cold sores (fever blisters) are caused by the herpes simplex virus (HSV), passed on through contact with infected skin or body...
-
Picture of Cold Sores Treatment
You can't cure HSV or a cold sore, but you can alleviate the pain it causes by avoiding spicy or acidic foods, applying ice, and...
-
Picture of Cold Sore and Canker Sore
Cold sores and canker sores aren't the same. See a picture of Cold Sore and Canker Sore and learn more about the health topic.
-
Picture of Cold Sore Between Nose and Mouth
Can a cold sore appear somewhere other than your lip? They are not as common, but cold sores can appear anywhere on the face,...
-
Picture of Cold Sores (Fever Blisters)
Cold sores, sometimes called fever blisters, are groups of small blisters on the lip and around the mouth. See a picture of Cold...
-
HIV and AIDS Rashes and Skin Conditions
A weakened immune system can let in the germs that cause skin conditions. Learn which skin problems are most common in people...
-
Sleep Disorders: Natural Sleep Aids & Supplements
Lots of people turn to these drug-free herbal remedies for a better night's rest. Learn about some of the most popular natural...
Related Disease Conditions
-
HIV Early Signs and Stages
HIV (human immunodeficiency virus) weakens your immune system. Some people with HIV don’t have any symptoms, but those that do may experience mononucleosis-like or flu-like symptoms. There are 3 stages of HIV.
-
Do Cold Sores Mean You Have an STD?
Having a cold sore does not necessarily mean you have an STD. Most cold sores are caused by herpes simplex virus type 1 (HSV-1), which typically is not transmitted by sexual contact.
-
Pimple vs. Cold Sore
Pimples are areas of skin inflammation with pus in the center. Cold sores are fluid-filled blisters. Pimples are caused by bacterial overgrowth and inflammation. Cold sores are caused by infection with herpes simplex viruses (HSV-1 and HSV-2). Benzoyl peroxide and sometimes antibiotics treat acne. Antiviral medications accelerate the healing process of oral herpes.
-
Cold Sores (Oral Herpes, Herpes Labialis)
Cold sores (labial herpes) are caused by herpes simplex virus type 1 infection and often appear on the mouth and lips. Read about treatment causes, symptoms, treatment, and diagnosis of oral herpes.
-
HIV and AIDS
Second Source article from WebMD
-
Cytomegalovirus (CMV)
Cytomegalovirus (CMV) is a virus that is spread from person to person via spit, semen, vaginal secretions, urine, blood, sexual contact, breastfeeding, blood transfusions, organ transplants, and breast milk. Symptoms of CMV include fatigue, swollen glands, fever, and sore throat. You can take precautions to prevent CMV such as washing hands frequently and thoroughly and using condoms. If you work in a daycare center, wash your hands thoroughly after contact with body secretions, and avoid oral contact with objects covered in saliva. Individuals with HIV infection are at most risk of contracting CMV.
-
How Do You Treat a Cold Sore in Your Nose?
Cold sores are a type of blister that may show up clear and then become cloudy. Treat a cold sore under your nose with home remedies, topical creams and ointments, and prescription medications.
-
What Is a Detectable HIV Viral Load? Normal Viral Load
Detectable viral load is defined as having more than 200 copies of the human immunodeficiency virus (HIV) per milliliter of blood.
-
What Foods Should HIV Patients Avoid?
People living with HIV face several health challenges because their bodies must work harder to fight infections. HIV patients should avoid foods high in sodium, sugar, and trans and saturated fats.
-
Can the HIV Virus Go Away?
There is no cure or vaccine for human immunodeficiency virus (HIV) infection; however, early treatment can help increase the life expectancy of infected people.
-
Are Cold Sores (Fever Blisters) Contagious?
About 20% of cases of cold sores are caused by herpes simplex virus type 2 (HSV-2), and approximately 80% of cold sores are caused by herpes simplex virus type 1 (HSV-1). Cold sores are transmitted by sharing utensils and razors, kissing, and oral sex. There is no cure for cold sores.
-
Can I Get HIV From Surfaces?
Studies proved that HIV cannot be transmitted through surfaces such as toilet seats, chairs, doorknobs, drinking glasses and bedsheets. The virus cannot survive outside a human host; hence, transmission through air, water (swimming pools), insect bite or casual contacts such as handshake, hug or touch is not possible.
-
Are Cold Sores the Same as Herpes?
What is the difference between cold sores and herpes? Cold sores are painful, unsightly sores that usually pop up around your mouth. Certain medications, home care and alternative therapies may help you get rid of cold sores fast.
-
How Do I Get Rid of a Cold Sore Overnight?
You cannot get rid of cold sores overnight. There is no cure for cold sores. However, to speed up the healing time of a cold sore, you can consult with your doctor and take prescription medications such as antiviral tablets and creams. A cold sore may go away without treatment within a week or two.
-
Genital Herpes and Cold Sores: 10 Myths and Facts
Genital herpes and cold sores (oral herpes) are the names given to two types of infection caused by the two types of herpes simplex virus (HSV): HSV-1 and HSV-2.
-
AIDS (Acquired Immunodeficiency Syndrome)
AIDS is the advanced stage of HIV infection. Symptoms and signs of AIDS include pneumonia due to Pneumocystis jiroveci, tuberculosis, toxoplasmosis, seizures, weakness, meningitis, yeast infection of the esophagus, and Kaposi's sarcoma. Anti-retroviral therapy (HAART) is used in the treatment of AIDS.
-
Is It Possible for HIV to Go Away on Its Own?
When a person contracts the human immunodeficiency virus (HIV), they are infected for life; however, early treatment can help them live normal lives.
-
HIV vs. AIDS
Human immunodeficiency virus causes HIV infection. Acquired immunodeficiency syndrome (AIDS) is a condition that results after HIV has extensively damaged a person's immune system. Risk factors for HIV and AIDS include use of contaminated needles or syringes, unprotected sex, STDs, receiving a blood transfusion prior to 1985 in the United States, having many sex partners, and transmission from a mother to her child.
-
Can HIV be Cured Naturally?
HIV stands for human immunodeficiency virus. If someone has HIV it means that they have been diagnosed with the HIV infection. AIDS (acquired immune deficiency syndrome); however, is the most advanced or final stage of the HIV infection. It is important to get tested for HIV in the early stages of infection to minimize the damage to the immune system. Successful treatment aims to reduce HIV load to a level that is harmless to the body.
-
Can I Test HIV Positive If My Viral Load is Undetectable?
You can still test positive for the human immunodeficiency virus (HIV) even if your viral load is undetectable.
-
Can I Get HIV From Casual Contact Like Hugging or Touching?
Human immunodeficiency virus (HIV) cannot spread through casual contact such as hugging or touching. HIV does not spread through urine, saliva, tears, sweat, kissing (closed mouth or social kissing), shaking hands, sharing utensils, sharing food or drinks, sharing clothes, or from toilet seats. HIV is spread through bodily fluids from a person with HIV.
-
HIV Medications List and Drug Charts
The ultimate goal of HIV treatment is getting the viral load down below detectable levels. As long as those viral load and antibody levels are below a proscribed range, people with HIV can stave off AIDS and other serious symptoms. Antiviral treatment options usually include combinations of two NRTIs, often referred to as "nucs," and a third drug, typically being a boosted protease inhibitor, a NNRTI, often called "non-nucs," and integrase strand transfer inhibitors.
-
Does HIV Have a Permanent Cure?
As of now, there is no permanent HIV cure, but antiretroviral treatment can effectively control HIV.
-
HIV/AIDS Infection Transmission and Prevention
HIV (human immunodeficiency virus) is spread through contact with genital fluids or blood of an infected person. The spread of HIV can occur when these secretions come in contact with tissues such as those lining the vagina, anal area, mouth, eyes (the mucus membranes), or with a break in the skin, such as from a cut or puncture by a needle.
-
HIV/AIDS Testing: Diagnosis and Monitoring
HIV/AIDS diagnosis and monitoring have come a long way from the days when a diagnosis was a death sentence. Crucial parts of the effective treatment regimens developed in the last 40 years are consistent monitoring of the viral load (the amount of virus in the blood), and the immune cell count, which function as biological markers of the disease’s progression. Doctors also must test for drug resistance.
-
How Did AIDS Start?
The human immunodeficiency virus (HIV) responsible for attacking the immune system is zoonotic, which means it is transferred to humans from nonhuman primates. The earliest known case of HIV-1 infection in human blood is from a sample taken in 1959.
-
HIV/AIDS Facts: What Is HIV?
HIV (human immunodeficiency virus) is the precursor infection to AIDS (acquired immunodeficiency syndrome). HIV is transmitted through blood and genital secretions; most people get it through sexual contact or sharing needles for illegal IV drug use. HIV can be controlled by a strict drug regimen, but left unchecked, it leads to AIDS. In AIDS, the immune system collapses and the body falls prey to secondary, opportunistic infections and cancers that typically kill the person.
-
How Long Is a Cold Sore Contagious?
Cold sores are blisters around your mouth and lips. Cold sores are contagious until they are completely healed.
-
What Are the Side Effects of HIV Medications?
It’s important to know the potential side effects of all the drugs you take to control your HIV infection, as well as potential drug interactions. All of the NNRTIs (nonnucleoside analogue reverse transcriptase inhibitors), for example, are associated with important drug-drug interactions so they must be used with caution in patients on other medications. Learn more about the side effects of the drugs in standard treatment regimens.
-
Does HIV Have Different Strains?
Human immunodeficiency virus (HIV) constantly replicates itself, resulting in multiple strains, which are mainly divided into two types (HIV-1 and HIV-2).
-
Can Herpes Simplex Be Cured?
The herpes simplex virus causes sores and blisters around the mouth or genitals. Learn the signs of herpes, what causes it, how doctors diagnose it, and what you can do to treat it.
-
HIV Life Expectancy and Long-term Outlook
With early diagnosis and proper treatment, people with HIV can live a healthy and long life. There is no generalized definitive period for which a person with HIV can live.
-
What Does HIV Do to a Person?
Human immunodeficiency virus (HIV) attacks and weakens the immune system, impairing the body's ability to fight diseases and infections.
-
What Can Trigger a Cold Sore?
After you get infected with HSV, it lies inactively in the nerve cells inside your skin and may appear as another cold sore at the same place as before.
-
When should you start HIV medication?
Nearly everyone who is infected with HIV (human immunodeficiency virus) should start antiviral medication therapy as soon as they are diagnosed. Older guidelines recommended delaying treatment to help reduce the potential for drug side effects and viral resistance to treatment. Current thinking theorizes that early treatment may preserve more of the body's immune function.
-
What Is the HIV Virus?
HIV (human immunodeficiency virus) is a virus that attacks and damages the immune system, which can lead to AIDS (acquired immunodeficiency syndrome) over time. Learn about types, symptoms, and treatments. Check out the center below for more medical references on HIV/AIDS, including multimedia (slideshows, images, and quizzes), related diseases, treatment, diagnosis, medications, and prevention or wellness.
-
Is HIV PEP (Post-Exposure Prophylaxis) Recommended for Me?
Post-exposure prophylaxis (PEP) refers to a short course of antiretroviral medications taken soon after a possible exposure to HIV to prevent the virus from infecting your body.
-
What Comes First HIV or AIDS?
HIV is an infectious that suppresses the immune system. Acquired Immunodeficiency Syndrome (AIDS) is the most severe stage of the infection caused by the Human Immunodeficiency Virus (HIV).
-
What Is the Difference Between HIV and AIDS?
HIV is a virus that causes immunosuppression. The difference between HIV and AIDS is that HIV is the first stage of the viral illness while AIDS represents the progression of the illness.
-
How Many HIV Treatments Are There?
Treatment for human immunodeficiency virus (HIV) often involves a combination of anti-HIV drugs. There are 7 HIV drug classes based on how they fight HIV.
-
How Do You Get a Cold Sore on Your Lip?
Cold sores, also called fever blisters or oral herpes, are a viral infection that leaves small blisters around your mouth. You get a cold sore on your lip due to viral infection from herpes simplex virus type 1 (HSV-1).
-
How Is HIV Currently Being Treated?
Treatment for human immunodeficiency virus (HIV) is ongoing and consists of various antiviral medication combinations (antiretroviral therapy).
Treatment & Diagnosis
- HIV-AIDS FAQs
- HIV Treatment, Medications, and Prevention
- Retrovirus & Opportunistic Infections Part II
- HIV Urine Test Approved
- HIV Treatment - To Interrupt or Not
- Unprotected Sex Between HIV-Infected Partners: What's the Harm?
- HIV Transmission and Progression to AIDS Continues
- Physical and Biochemical Changes in HIV Disease
- Babies On The Breast Of HIV Moms
- Generic AIDS Drug Effective - And Now?
- Can HIV Cause Kaposi's Sarcoma?
- Do You Need Antiretroviral Therapy for HIV with No Symptoms?
- Does HIV Cause Colorectal Cancer?
- Does Anti-Retroviral Therapy for HIV Cause Diabetes?
- How Long Should You Wait to Get an HIV Test?
- What Liver Problems Does HIV Cause?
- Can You Treat Hepatitis B With Aids Drug Lamivudine?
- Does Circumcision Prevent HIV and AIDS?
- HIV Infection Facts, History, Causes, and Risk Factors
- Cold Sore Treatment
- HIV Tests, Symptoms, Signs, and Stages of Infection
- Baby "Cured" of HIV Infection
Medications & Supplements
Prevention & Wellness

Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
https://reference.medscape.com/drug/foscavir-phosphonoformic-acid-foscarnet-342614