Foscarnet Injection


Foscarnet injection is used alone or with ganciclovir (Cytovene) to treat cytomegalovirus (CMV) retinitis (an eye infection that can cause blindness) in people who have human immunodeficiency virus (HIV) infection. Foscarnet injection is also used to treat herpes simplex virus (HSV) infections of the skin and mucus membranes (mouth, anus) in people whose immune system is not working normally and when treatment with acyclovir did not help. Foscarnet is in a class of medications called antivirals. It works by slowing the growth of CMV and HSV. Foscarnet controls CMV retinitis and HSV infections of the skin and mucus membranes but does not cure these infections.

Side Effects Of Foscarnet Injection

Foscarnet may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:

  • itching, redness, pain, or swelling in the place where you received your injection
  • nausea
  • stomach pain
  • back pain
  • loss of appetite or weight
  • constipation
  • headache
  • vision changes
  • redness, irritation, or sores on the penis
  • redness, irritation, or sores around the vagina

Some side effects can be serious. If you experience any of these symptoms or those listed in the WARNINGS section, call your doctor immediately or get emergency medical treatment:

  • rash
  • hives
  • swelling of the eyes, face, lips, tongue, or throat
  • difficulty breathing or swallowing
  • chest pain
  • fast, pounding, or irregular heartbeat
  • fainting
  • lightheadedness
  • loss of consciousness
  • vomiting
  • diarrhea
  • fever, chills, cough, or other signs of infection
  • unusual bleeding or bruising
  • black and tarry stools
  • bloody vomit or vomited material that looks like coffee grounds
  • pale skin
  • shortness of breath
  • confusion
  • muscle pain or cramps
  • increased sweating

Foscarnet may cause other side effects. Call your doctor if you have any unusual problems while using this medication.

Warnings & Precautions

Before using foscarnet injection:

  • tell your doctor and pharmacist if you are allergic to foscarnet, any other medications, or any of the ingredients in foscarnet injection. Ask your pharmacist for a list of the ingredients.
  • tell your doctor and pharmacist what other prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Be sure to mention the medications listed in the WARNINGS section and any of the following: amiodarone (Cordarone, Nexterone, Pacerone); azithromycin (Zithromax); clarithromycin (Biaxin); diuretics (‘water pills’) such as bumetanide, ethacrynic acid (Edecrin), furosemide (Lasix), or torsemide (Demadex); dofetilide (Tikosyn); erythromycin (E-mycin, Ery-Tab, others); fluoroquinolone antibiotics including ciprofloxacin (Cipro), gatifloxacin (Tequin), levofloxacin (Levaquin), moxifloxacin (Avelox), and ofloxacin (Floxin); medications for mental illness or nausea; procainamide; quinidine (in Nuedexta); ritonavir (Norvir, in Kaletra); saquinavir (Invirase); sotalol (Betapace, Sorine); and tricyclic antidepressants (‘mood elevators’) such as amitriptyline, desipramine (Norpramin), doxepin (Silenor), or nortriptyline (Pamelor). Your doctor may need to change the doses of your medications or monitor you carefully for side effects. Many other medications may also interact with foscarnet injection, so be sure to tell your doctor about all the medications you are taking, even those that do not appear on this list.
  • tell your doctor if you have or have ever had QT prolongation (an irregular heart rhythm that can lead to fainting, loss of consciousness, seizures, or sudden death); low levels of potassium or magnesium in your blood; heart disease; or if you are on a low salt diet.
  • tell your doctor if you are pregnant, plan to become pregnant, or are breastfeeding. If you become pregnant while receiving foscarnet injection, call your doctor.
  • you should know that foscarnet may make you drowsy or dizzy. Do not drive a car or operate machinery until you know how this medication affects you.

Foscarnet Injection Dosage

Foscarnet injection comes as a liquid to be intravenously (into a vein). It is usually infused slowly over 1 to 2 hours every 8 or 12 hours. The length of your treatment depends on how you respond to the medication.

You may receive foscarnet injection in a hospital or you may administer the medication at home. If you will be receiving foscarnet injection at home, your healthcare provider will show you how to use the medication. Be sure that you understand these directions, and ask your healthcare provider if you have any questions

Ask your pharmacist or doctor for a copy of the manufacturer’s information for the patient.


It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.


All information has been provided courtesy of MedLinePlus from the National Library of Medicine and from the FDA.