Pronunciation:

fos-KAR-net

Brand Names:

• Foscavir

Dosage Forms:

• Solution

Warnings:

Renal impairment is the major toxicity of foscarnet. Frequent monitoring of serum creatinine, with dose adjustment for changes in renal function, and adequate hydration with administration of foscarnet is imperative. Seizures, related to alteration in plasma minerals and electrolytes, have been associated with foscarnet treatment. Therefore, patients must be carefully monitored for such changes and their potential sequelae. Mineral and electrolyte supplementation may be required. Foscarnet is indicated for use only in immunocompromised patients with cytomegalovirus retinitis and mucocutaneous acyclovir-resistant herpes simplex virus infections .

Classifications:

Therapeutic—

Antiviral

Pharmacologic—

Pyrophosphate Analog

Uses of This Medicine:

Foscarnet injection is used to treat symptoms of cytomegalovirus (CMV) infection of the eyes in patients with acquired immune deficiency syndrome (AIDS). Foscarnet will not cure CMV eye infection, but it may help to control worsening of the symptoms. This medicine is also used to treat herpes simplex virus (HSV) infections of the skin and mucous membranes in people who are immunocompromised and whose infections did not improve with other treatment. Foscarnet may also be used for other serious viral infections as determined by your doctor. However, it does not work in treating certain viruses, such as the common cold or the flu.

This medicine is to be given only by or under the direct supervision of your doctor.

Before Using This Medicine:

In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For this medicine, the following should be considered:

Allergies—

Tell your doctor if you have ever had any unusual or allergic reaction to this medicine or any other medicines. Also tell your health care professional if you have any other types of allergies, such as to foods, dyes, preservatives, or animals. For non-prescription products, read the label or package ingredients carefully.

Children—

Appropriate studies have not been performed on the relationship of age to the effects of foscarnet injection in the pediatric population. Safety and efficacy have not been established.

Older adults—

Appropriate studies performed to date have not demonstrated geriatric-specific problems that would limit the usefulness of foscarnet injection in the elderly. However, elderly patients are more likely to have age-related kidney problems, which may require caution and an adjustment in the dose for patients receiving foscarnet injection.

Breast-feeding—

There are no adequate studies in women for determining infant risk when using this medication during breastfeeding. Weigh the potential benefits against the potential risks before taking this medication while breastfeeding.

Other medicines—

Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are receiving this medicine, it is especially important that your healthcare professional know if you are taking any of the medicines listed below. The following interactions have been selected on the basis of their potential significance and are not necessarily all-inclusive.

Using this medicine with any of the following medicines is not recommended. Your doctor may decide not to treat you with this medication or change some of the other medicines you take.

• Arsenic Trioxide
• Bepridil
• Cisapride
• Dronedarone
• Levoketoconazole
• Levomethadyl
• Mesoridazine
• Pimozide
• Piperaquine
• Probucol
• Saquinavir
• Sparfloxacin
• Terfenadine
• Thioridazine
• Ziprasidone

Using this medicine with any of the following medicines is usually not recommended, but may be required in some cases. If both medicines are prescribed together, your doctor may change the dose or how often you use one or both of the medicines.

• Acecainide
• Acyclovir
• Adagrasib
• Ajmaline
• Alfuzosin
• Amikacin
• Amiodarone
• Amisulpride
• Amitriptyline
• Amoxapine
• Amphotericin B
• Anagrelide
• Apomorphine
• Aprindine
• Aripiprazole
• Aripiprazole Lauroxil
• Asenapine
• Aspirin
• Astemizole
• Atazanavir
• Azimilide
• Azithromycin
• Bedaquiline
• Bretylium
• Bumetanide
• Buprenorphine
• Bupropion
• Buserelin
• Capreomycin
• Ceritinib
• Chloral Hydrate
• Chloroquine
• Chlorpromazine
• Cidofovir
• Ciprofloxacin
• Citalopram
• Clarithromycin
• Clofazimine
• Clomipramine
• Clothiapine
• Clozapine
• Crizotinib
• Cyclobenzaprine
• Cyclosporine
• Dabrafenib
• Dasatinib
• Degarelix
• Delamanid
• Desipramine
• Deslorelin
• Deutetrabenazine
• Dexmedetomidine
• Dibekacin
• Dibenzepin
• Disopyramide
• Dofetilide
• Dolasetron
• Domperidone
• Donepezil
• Doxepin
• Droperidol
• Ebastine
• Efavirenz
• Encainide
• Encorafenib
• Enflurane
• Entrectinib
• Eribulin
• Erythromycin
• Escitalopram
• Ethacrynic Acid
• Etrasimod
• Famotidine
• Felbamate
• Fexinidazole
• Fingolimod
• Flecainide
• Fluconazole
• Fluoxetine
• Formoterol
• Fosphenytoin
• Fostemsavir
• Framycetin
• Furosemide
• Galantamine
• Gatifloxacin
• Gemifloxacin
• Gentamicin
• Gepirone
• Glasdegib
• Gonadorelin
• Goserelin
• Granisetron
• Halofantrine
• Haloperidol
• Halothane
• Histrelin
• Hydroquinidine
• Hydroxychloroquine
• Hydroxyzine
• Ibutilide
• Iloperidone
• Imipramine
• Inotuzumab Ozogamicin
• Isepamicin
• Isoflurane
• Isradipine
• Itraconazole
• Ivabradine
• Ivosidenib
• Kanamycin
• Ketoconazole
• Lapatinib
• Lefamulin
• Lenvatinib
• Leuprolide
• Levofloxacin
• Lidoflazine
• Lofexidine
• Lorcainide
• Lumefantrine
• Macimorelin
• Mefloquine
• Methadone
• Methotrexate
• Methotrimeprazine
• Metronidazole
• Mifepristone
• Mirtazapine
• Mizolastine
• Mobocertinib
• Moricizine
• Moxifloxacin
• Nafarelin
• Nelfinavir
• Neomycin
• Netilmicin
• Nilotinib
• Norfloxacin
• Nortriptyline
• Octreotide
• Ofloxacin
• Olanzapine
• Ondansetron
• Osilodrostat
• Osimertinib
• Oxaliplatin
• Ozanimod
• Pacritinib
• Paliperidone
• Panobinostat
• Papaverine
• Paromomycin
• Paroxetine
• Pasireotide
• Pazopanib
• Pentamidine
• Perphenazine
• Phenobarbital
• Pimavanserin
• Pipamperone
• Pirmenol
• Pitolisant
• Ponesimod
• Posaconazole
• Prajmaline
• Primidone
• Procainamide
• Prochlorperazine
• Promethazine
• Propafenone
• Protriptyline
• Quetiapine
• Quinidine
• Quinine
• Quizartinib
• Ranolazine
• Relugolix
• Ribociclib
• Risperidone
• Ritonavir
• Selpercatinib
• Sematilide
• Sertindole
• Sertraline
• Sevoflurane
• Siponimod
• Sisomicin
• Sodium Phosphate
• Sodium Phosphate, Dibasic
• Sodium Phosphate, Monobasic
• Solifenacin
• Sorafenib
• Sotalol
• Spectinomycin
• Spiramycin
• Streptomycin
• Sulfamethoxazole
• Sulpiride
• Sultopride
• Sunitinib
• Tacrolimus
• Tamoxifen
• Tedisamil
• Telaprevir
• Telavancin
• Telithromycin
• Tetrabenazine
• Tobramycin
• Tolterodine
• Toremifene
• Torsemide
• Trazodone
• Triclabendazole
• Trifluoperazine
• Trimethoprim
• Trimipramine
• Triptorelin
• Valacyclovir
• Vandetanib
• Vardenafil
• Vemurafenib
• Venlafaxine
• Vilanterol
• Vinflunine
• Voclosporin
• Voriconazole
• Vorinostat
• Zolmitriptan
• Zotepine
• Zuclopenthixol

Other interactions—

Certain medicines should not be used at or around the time of eating food or eating certain types of food since interactions may occur. Using alcohol or tobacco with certain medicines may also cause interactions to occur. Discuss with your healthcare professional the use of your medicine with food, alcohol, or tobacco.

Other medical problems—

The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:

• Anemia or
• Electrolyte or mineral imbalance (eg, low calcium, phosphorus, magnesium, or potassium) or
• Granulocytopenia (a low number of certain white blood cells) or
• Heart disease or
• Seizures—Use with caution. May make these conditions worse.

• Dehydration or
• Kidney disease—Use with caution. May have an increased risk for more serious side effects.

• Patients who are on a controlled sodium diet—Avoid foscarnet injection in patients with this condition.

Proper Use of This Medicine:

A nurse or other health professional will give you this medicine in a hospital. This medicine is given through a needle placed in one of your veins. The medicine must be injected slowly, so your IV tube will need to stay in place for at least 1 to 2 hours.

This medicine may damage your kidneys. To help prevent this, you may have extra liquids given into your vein before or with your treatment. Your doctor may also want you to drink extra liquids while you are being given this medicine.

To ensure the best response, foscarnet must be given for the full time of treatment. Also, this medicine works best when there is a constant amount in the blood. To help keep the amount constant, foscarnet must be given on a regular schedule.

Precautions While Using This Medicine:

It is very important that your doctor check your progress at regular visits. This will allow your doctor to see if the medicine is working properly. Blood and urine tests may be needed to check for unwanted effects.

This medicine may cause serious allergic reactions, including anaphylaxis. Anaphylaxis can be life-threatening and requires immediate medical attention. Call your doctor right away if you have a rash, itching, trouble breathing, trouble swallowing, or any swelling of your hands, face, or mouth while you are using this medicine.

Contact your doctor right away if you have any changes to your heart rhythm. You might feel dizzy or faint, or you might have a fast, pounding, or uneven heartbeat. Make sure your doctor knows if you or anyone in your family has ever had a heart rhythm problem such as QT prolongation.

This medicine may cause sores on the genitals (sex organs). Washing your genitals after urination may decrease the chance of your developing this problem.

It is also very important that your ophthalmologist (eye doctor) check your eyes at regular visits since you may have some loss of eyesight due to retinitis even while you are receiving foscarnet injection.

This medicine may make you dizzy. Do not drive or do anything else that could be dangerous until you know how this medicine affects you.

Do not take other medicines unless they have been discussed with your doctor. This includes prescription or nonprescription (over-the-counter [OTC]) medicines and herbal or vitamin supplements.

Side Effects of This Medicine:

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor or nurse immediately if any of the following side effects occur:

More common

Increased or decreased frequency of urination or amount of urine

increased thirst

Less common

Chills

convulsions

fever

muscle twitching

pain at the injection site

pain or numbness in hands or feet

tingling sensation around the mouth

tremor

unusual tiredness and weakness

Rare

Sores or ulcers on the mouth or throat, penis, or vulva

Incidence not known

Difficulty with breathing or swallowing

fainting

hives or welts, itching, or skin rash

irregular heartbeat recurrent

large, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs

nausea

reddening of the skin, especially around the ears

swelling of the eyes, face, or inside of the nose

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

Abdominal or stomach pain

anxious feeling

confusion

dizziness

headache

loss of appetite

nausea and vomiting

unusual tiredness or weakness

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.