Foscarnet Injection
Foscarnet is an antiviral medicine given by intravenous infusion to treat CMV retinitis in people with AIDS and acyclovir-resistant herpes (HSV) skin and mucous membrane infections in immunocompromised patients.
🧬 Where this information comes from Click to expand
The clinical label records used on this page are FDA-filed Structured Product Labeling (SPL) retrieved through openFDA. We identified 10 clinical label sets within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. Forms, routes, brands, labelers, strengths, and NDC product-record counts are built separately from matching FDA National Drug Code Directory records. The linked DailyMed document is a representative official source for verification, not the page’s only clinical source. View the linked label on DailyMed →
⚠️ FDA Boxed Warning — the FDA’s strongest safety alert ▾
Kidney damage is the number-one risk of foscarnet sodium injection and requires close monitoring throughout treatment. Blood tests to check kidney function must be done frequently, and the dose must be adjusted if kidney function changes. Drinking adequate fluids and receiving IV hydration with each infusion is essential to protect the kidneys.
Foscarnet has also been linked to seizures, caused by shifts in calcium and other minerals in the blood. Patients must be monitored for electrolyte changes, and supplements may be needed. This medication is approved only for immunocompromised patients — specifically those with CMV retinitis or acyclovir-resistant HSV skin/mucous membrane infections.
📖 Foscarnet Injection: Patient Information Guide
A plain-language walkthrough of Foscarnet Injection — what it treats, how it works, how it’s taken, side effects, warnings and interactions. Tap any section to expand it.
🎯What it's used for▾
Foscarnet sodium injection (brand: Foscavir) is an antiviral given intravenously, approved only for immunocompromised patients with specific viral infections.
- CMV retinitis in AIDS patients: Foscavir treats this serious viral eye infection that can lead to blindness.
- Relapsed CMV retinitis: Foscavir in combination with ganciclovir is approved for patients whose CMV retinitis has returned after treatment with either drug alone.
- Acyclovir-resistant mucocutaneous HSV infections: Foscavir treats herpes sores on the skin or mucous membranes in immunocompromised patients when acyclovir no longer works.
Foscavir is not approved for CMV infections in other organs (such as the lungs or gut), congenital or neonatal CMV or HSV, HSV in the eye or brain, or any of these infections in people with healthy immune systems.
⚙️How it works▾
Foscarnet works by directly blocking a critical site — called the pyrophosphate binding site — on the enzymes viruses use to copy their DNA (called DNA polymerases). By blocking this site, foscarnet prevents the virus from replicating. Crucially, foscarnet does not need to be converted into an active form inside cells, which is how drugs like acyclovir work. This means foscarnet can still work against viruses that have mutated and become resistant to acyclovir.
Because foscarnet targets a virus-specific enzyme rather than a human one, it selectively attacks the virus at concentrations that don't harm the body's own DNA-copying machinery.
💊How it's taken▾
Foscavir is given only as a controlled intravenous infusion — never as a fast or direct injection. Treatment is divided into two phases:
- Induction phase: Given multiple times daily over 2–3 weeks (or until HSV sores heal), depending on the condition being treated.
- Maintenance phase (CMV retinitis): Switched to a once-daily infusion after induction is complete.
Every dose is individually calculated based on kidney function and body weight. An infusion pump is always required. IV hydration fluids are given before the first infusion and alongside each subsequent dose. Follow your prescriber's schedule exactly — do not adjust frequency or timing on your own.
🤒Side effects — in detail▾
Foscarnet has a wide range of possible side effects; the most important to know about are listed below.
- Fever
- Nausea, vomiting, diarrhea
- Anemia (low red blood cells)
- Headache
- Reduced kidney function
- Tingling or numbness, especially around the mouth or in the limbs (sign of low calcium)
- Low levels of calcium, magnesium, or potassium in the blood
- Rash and increased sweating
Serious reactions that need immediate medical attention include seizures, severe kidney function decline, dangerous heart rhythm changes (QT prolongation), and severe allergic reactions such as anaphylactic shock. Seizures — sometimes fatal — have occurred and are linked to electrolyte imbalances.
⚠️Warnings & precautions▾
- Kidney damage: This is the biggest risk. Nearly all patients experience some kidney function decline. Monitoring is required 2–3 times per week during induction and weekly during maintenance. Doses must be adjusted when kidney function changes. IV hydration before and during every infusion is essential.
- Electrolyte imbalances: Foscarnet can cause dangerously low calcium, magnesium, and potassium, and abnormal phosphate levels. These can cause seizures, muscle spasms, and heart rhythm problems. Report tingling around the mouth or in the limbs, muscle cramps, or irregular heartbeat immediately.
- Seizures: Linked to electrolyte abnormalities — some cases have been fatal or resulted in status epilepticus (prolonged seizure). Risk is higher in patients with pre-existing kidney impairment, low calcium, or neurological conditions.
- QT prolongation and torsades de pointes: Foscarnet can alter the heart's electrical rhythm in a way that may cause a dangerous arrhythmia. An ECG should be checked before and during treatment.
- Serious allergic reactions: Anaphylactic shock and severe hypersensitivity have been reported. If this occurs, treatment must be stopped immediately.
🔀What it interacts with▾
Foscarnet has several important drug interactions — tell your care team about everything you take.
- IV pentamidine: Combining these can cause life-threatening drops in blood calcium — avoid unless absolutely necessary.
- Nephrotoxic drugs (aminoglycosides, amphotericin B, cyclosporine, acyclovir, methotrexate, tacrolimus, IV pentamidine): All increase risk of kidney damage when combined with foscarnet.
- QT-prolonging drugs (quinidine, procainamide, dofetilide, amiodarone, sotalol, phenothiazines, tricyclic antidepressants, certain macrolide antibiotics and fluoroquinolones): Combining these raises the risk of dangerous heart rhythm disturbances.
- Loop diuretics (e.g., furosemide): May reduce foscarnet clearance and increase toxicity; thiazide diuretics are preferred if a water pill is needed.
- Ritonavir or ritonavir plus saquinavir: Kidney problems have been reported with these HIV drug combinations.
- Drugs incompatible in the IV line: Foscarnet must not share an IV line with many drugs including acyclovir, ganciclovir, amphotericin B, calcium-containing solutions, diazepam, phenytoin, vancomycin, and others — a dedicated line is required.
This is not a complete list of interactions. Always talk with your doctor or pharmacist before starting, stopping, or changing any medication.
📋Before taking it▾
- Do not use foscarnet if you have a known allergy to foscarnet sodium.
- Tell your doctor if you have any kidney disease — doses must be carefully adjusted and monitoring is intensive.
- Foscarnet is not recommended for patients on hemodialysis; dosing guidelines have not been established.
- Tell your doctor about any heart rhythm problems, history of QT prolongation, or if you take heart medications.
- Tell your doctor about any electrolyte abnormalities, especially low calcium, magnesium, or potassium.
- Tell your doctor about all medications, including antivirals, antibiotics, antifungals, HIV drugs, and diuretics.
- This drug is approved only for immunocompromised individuals — it should not be used in people with healthy immune systems.
🚑If you take too much▾
Taking too much foscarnet can worsen its known risks: kidney damage, dangerous electrolyte shifts (especially calcium and phosphate), seizures, and tingling or numbness in the limbs. There is no specific antidote. If an overdose is suspected, treatment focuses on monitoring kidney function and electrolytes, and may include IV fluids or hemodialysis to help clear the drug — though the effectiveness of these approaches has not been formally studied.
📡Pharmacodynamics — effects in the body▾
Foscarnet works by selectively blocking the pyrophosphate binding site on virus-specific DNA polymerases — the enzymes viruses need to copy their genetic material. At the concentrations used clinically, it does not significantly affect the body's own DNA polymerases. This selective action allows it to stop viral replication without directly interfering with normal human cell function. Because it does not require activation by thymidine kinase, it remains active against viral strains that have developed resistance through mutations in that enzyme.
🔬Pharmacokinetics — how your body processes it▾
Foscarnet is given intravenously and distributes throughout the body, including into the fluid surrounding the brain and spinal cord (CSF), reaching about two-thirds of plasma levels there. It is only about 14–17% bound to proteins in the blood. The drug is cleared almost entirely by the kidneys, so any reduction in kidney function significantly slows its elimination and raises blood levels — making dose adjustment essential. Foscarnet also deposits into bone, which accounts for its longer terminal elimination half-life (around 87 hours by urinary measurement) compared to its initial plasma half-life of roughly 3–4 hours.
📦How to store it▾
Store at 20° to 25°C (68° to 77°F). Protect from excessive heat (above 40°C) and from freezing. refrigerated or exposed to temperatures below the freezing point, precipitation may occur.
📄 Written from Foscarnet Injection’s FDA-approved label information, summarized in plain language with AI, and reviewed by our pharmacy team before publication. Every point is grounded in that labeling — nothing is invented. How we use AI →
Supplements & herbs that interact with Foscarnet Injection
12 supplements and herbal products have documented interactions with Foscarnet Injection in the licensed clinical database we use. Most are manageable — but your pharmacist should know about everything you take, including vitamins and herbals.
- Major · 2
- Moderate · 9
- Minor · 1
Educational information from a licensed clinical database (Natural Medicines) — see our data sources & update cadence. Not medical advice: an interaction being documented does not mean it will happen to you; do not start or stop medications or supplements without professional guidance.
Nutrient depletion considerations
Foscarnet Injection has been associated with lower levels of 1 nutrient in the clinical literature. This does not mean a deficiency will occur — it means these may be worth discussing with your pharmacist or healthcare provider, especially with long-term use.
Educational information from a licensed clinical database (Natural Medicines) — not medical advice. Do not start or stop medications or supplements without professional guidance.
🩺 Pharmacist Counseling Corner
Quick, plain-English answers to the questions patients ask most about Foscarnet Injection — the kind of thing our pharmacy team would talk through with you at the counter.
Why do I need to stay hydrated during every infusion? ▾
What does the tingling around my mouth mean? Should I be worried? ▾
Why do I need so many blood tests during treatment? ▾
Can I take my other medications while I'm getting foscarnet? ▾
What side effects are most likely, and which ones mean I should call someone right away? ▾
Why is foscarnet used instead of acyclovir for my herpes infection? ▾
Is Foscarnet Injection available over the counter? ▾
When was Foscarnet Injection first available? ▾
Who makes Foscarnet Injection? ▾
💬 Answers drafted from Foscarnet Injection’s FDA-approved label information, summarized in plain language with AI, and reviewed by our pharmacy team before publication. Grounded in that labeling — nothing is made up. How we use AI →
🧰 Keep exploring
💊 How Foscarnet Injection comes
Foscarnet Injection is available in 1 form. Different forms and brands can have different approved uses, doses, schedules, and directions. Follow the instructions for your exact product, and do not switch forms without guidance from your prescriber or pharmacist.
Injection
How this form is used
- Foscavir is used to treat CMV retinitis in patients with AIDS
- Foscavir is used in combination with ganciclovir for CMV retinitis that has relapsed after monotherapy with either drug
- Foscavir is used to treat acyclovir-resistant mucocutaneous HSV infections in immunocompromised patients
- Foscavir must always be given as a slow IV infusion using an infusion pump — never as a rapid or bolus injection
- Foscavir can be infused through a central venous line at 24 mg/mL; when given through a peripheral (arm) vein, it must be diluted to 12 mg/mL with normal saline or 5% dextrose to avoid vein irritation
- Foscavir must not be mixed in the same IV line as other drugs — use a dedicated line with only normal saline or 5% dextrose
- IV hydration fluids should be given before the first Foscavir infusion and alongside every subsequent infusion to help protect the kidneys
📊 Foscarnet Injection across the U.S. market
How Foscarnet Injection appears in the FDA’s National Drug Code Directory — including its dosage forms, strengths, brand names, manufacturers, and FDA-listed product records. These are directory records, not sales or prescription volume.
Share of FDA-listed product records by manufacturer — FDA National Drug Code Directory. Record counts are not sales or prescription volume.
📈 How widely Foscarnet Injection is used
A general measure of how commonly Foscarnet Injection is prescribed, based on Medicaid — one of the largest public drug programs. The figure below is prescriptions filled in Q1–Q4 2025, summed across every form and brand of the drug.
Think of this as a proxy for how widely Foscarnet Injection is used, drawn from freely available public data. Medicaid is just one program — these numbers don’t include Medicare, other government coverage, or commercial and cash-pay prescriptions, so real-world use is higher than what’s shown here.
How commonly is Foscarnet Injection prescribed? Of the 1,594 medications we measure, Foscarnet Injection ranks #1,511 by Medicaid prescriptions — more than 5% of them.
Utilization by Foscarnet Injection product
Pick a product to see its own Medicaid numbers. Each chip is one clinical product — a specific strength & dosage form as defined by RxNorm — with brand-name and generic versions combined.
250 ML foscarnet sodium 24 MG/ML Injection
Summed across the 2 of 18 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 1734377
Shares are of the Medicaid prescriptions shown here. Product grouping follows RxNorm (the National Library of Medicine’s drug terminology), so “one product” means one strength & dosage form regardless of manufacturer. Dollar figures are gross Medicaid reimbursement before mandatory rebates — rebates (often large, especially for brand-name drugs) are confidential, so actual net cost to Medicaid is lower than shown.
Source: Medicaid State Drug Utilization Data (CMS), aggregated by generic ingredient — summed across every NDC (all brands, strengths, salt forms and dosage forms) of Foscarnet Injection, and across all states and both fee-for-service and managed-care claims. A general popularity signal; it excludes Medicare, commercial insurance and cash prescriptions, so it is not total U.S. use. Based on the 2 of 18 listed Foscarnet Injection NDCs with Medicaid activity.
🔍 Compare Foscarnet Injection products
A representative set of FDA-listed product records for Foscarnet Injection — across manufacturers, strengths, and dosage forms, grouped by form with each product’s manufacturer and how the FDA approved it. The same medicine may be made and packaged by different companies, so a single drug can have many directory entries. (It’s also why a refill can look different — a new shape, color, or box — even though it contains the same medication.)
| Strength | Route | Manufacturer / Labeler | Category ⓘ | Details |
|---|---|---|---|---|
| 💊Injection | ||||
| 24 mg/mL | Intravenous | Amneal Pharmaceuticals LLC × 2 listings | ANDA | View NDC → |
| 6000 mg/250 mL | Intravenous | Baxter Healthcare Corporation × 2 listings | ANDA | View NDC → |
| 24 mg/mL | Intravenous | Caplin Steriles Limited | ANDA | View NDC → |
| 24 mg/mL | Intravenous | Clinigen Limited × 8 listings | NDA | View NDC → |
| 24 mg/mL | Intravenous | Fresenius Kabi USA, LLC | ANDA | View NDC → |
| 24 mg/mL | Intravenous | Gland Pharma Limited | ANDA | View NDC → |
| 24 mg/mL | Intravenous | Heritage Pharmaceuticals Inc. d/b/a Avet Pharmaceuticals Inc. × 2 listings | ANDA | View NDC → |
| 24 mg/mL | Intravenous | Hikma Pharmaceuticals USA Inc. | ANDA | View NDC → |
| 24 mg/mL | Intravenous | Sagent Pharmaceuticals | ANDA | View NDC → |
Showing 19 of 19 products — FDA National Drug Code Directory. See every product, package size and price: browse all 19 Foscarnet Injection NDCs →
📈 What people report — real-world data (FDA FAERS)
After a medicine reaches the market, patients, doctors and drugmakers can send the FDA reports of problems they think may be linked to it. Here’s what’s been reported for Foscarnet Injection — a signal of what to watch for, not proof the drug caused it.
Source: openFDA, from the FDA Adverse Event Reporting System (FAERS). These are voluntary reports — they don’t prove the drug caused the effect, and counts reflect how often something was reported, not how often it actually happens. Reports also often name the very problem the medicine is taken for — a common reason to file one is that the drug didn’t help — so for a pain reliever you may see “pain” high on the list; that points to why the report was filed, not to the drug causing the symptom. This counts every report that lists Foscarnet Injection in any role, so the total runs higher than the FDA’s official dashboard, which counts only cases where the drug is the suspect. For the authoritative figures, see the FDA FAERS Public Dashboard. Always talk to your pharmacist or doctor.
🏛️ The road to your pharmacy
How Foscarnet Injection went from FDA review to the pharmacy shelf — the key milestones in its regulatory journey.
Source: Drugs@FDA.
🚨 Recall history
A recall is when a specific batch of a medicine is pulled from the market — usually a manufacturing issue, not a problem with the drug itself. Class I is most serious, Class III least.
Source: openFDA drug enforcement (recall) reports.
RxNorm Concept Web — From Ingredient to Every Form and Strength
This page starts with one ingredient concept (IN). The branches below show its dose-form concepts (SCDF), then the available clinical drug and strength concepts (SCD). Combination products remain separate concepts with their own pages.
RxCUI 33562 1 dose form · 1 strength
-
Dose form (SCDF) Injection RxCUI 1734376In current FDA listingsClinical drug / strength (SCD) 250 ML foscarnet sodium 24 MG/MLRxCUI 1734377
Look up RxCUI 33562 in the RxCUI Atlas →
RxNorm is the U.S. National Library of Medicine’s normalized drug vocabulary. Its concept hierarchy can include forms that are not currently marketed; the status on each branch compares that concept with current FDA listings. RxCUIs identify vocabulary concepts, not individual packages or manufacturers.
📦 Supply & shortage status
Whether Foscarnet Injection is in short supply in the U.S. right now, plus any shortage history the FDA has on record. A shortage usually reflects a manufacturing or demand issue — not a safety problem with the drug.
Source: openFDA, from the FDA Drug Shortages database.
🏷️ Sold under these brand names
🏭 Manufacturers & labelers
RxNorm drug class
Foscarnet Injection belongs to the Pyrophosphate Analog DNA Polymerase Inhibitor class.
Classified by RxNorm RxClass — the U.S. National Library of Medicine's standardized drug-classification service (Established Pharmacologic Class from the FDA, the ATC drug family from the WHO, and mechanism of action). Reference only, not medical advice.
🔬 Where this comes from
Core label, product, RxNorm, safety, and utilization data on this page come from the sources identified below. AI-written, editorial, and licensed sections are labeled separately.
How we combine label and product data
HelloPharmacist combines public FDA and NLM records; we don’t author the underlying clinical facts. We identified 10 FDA-filed SPL label sets within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. The representative label is the starting point for the displayed reference monograph; the 12 largest stored in-scope SPL records, which may include that representative, are compared section by section, and the longest available version of each section is retained. Forms, routes, brands, labelers, product-listed strengths, and product-record counts are aggregated separately from ingredient-matched FDA NDC Directory records; package records listed above are associated with the linked SPL; and the normalized concept hierarchy comes from NLM RxNorm.
Where a section is identified as AI-written, its plain-language text is generated from bounded label evidence. New draft drug pages remain in the admin review queue before first publication. Clinigen Limited is the representative DailyMed label linked for verification and dates; it is not the sole source used for the page.
This is general education, not medical advice — always consult your doctor or pharmacist about your medications and any medical condition. For the exact wording of the linked representative label, view that label on DailyMed; some displayed composite sections may come from other in-scope SPL labels. Learn how we use AI and our data sources & update cadence.