Foscarnet: uses, dosing, side effects & brands
Foscarnet is a pyrophosphate analog dna polymerase inhibitor sold in the U.S. under 2 brand and generic names, for cytomegalovirus infections and herpes genitalis. Below: what the FDA label says, every product that contains it, what the pills look like, and its recall record.
Key facts
- Drug class
- Pyrophosphate Analog Dna Polymerase Inhibitor
- Treats (across its forms)
- Cytomegalovirus Infections and Herpes Genitalis
- Available as
- Injectable · Solution
- Sold as
- 2 products — Foscarnet Sodium and Foscavir
- Prescription?
- Prescription only
- Generic available?
- Yes
- Boxed warning
- Boxed warning
How foscarnet is dosed
From the FDA label for Foscarnet Sodium (application ANDA212483). Other foscarnet products — different forms, different strengths — are dosed differently. Follow the label for the one you were prescribed.
CAUTION—DO NOT ADMINISTER FOSCARNET SODIUM INJECTION BY RAPID OR BOLUS INTRAVENOUS INJECTION. THE TOXICITY OF FOSCARNET SODIUM INJECTION MAY BE INCREASED AS A RESULT OF EXCESSIVE PLASMA LEVELS. CARE SHOULD BE TAKEN TO AVOID UNINTENTIONAL OVERDOSE BY CAREFULLY CONTROLLING THE RATE OF INFUSION. THEREFORE, AN INFUSION PUMP MUST BE USED. IN SPITE OF THE USE OF AN INFUSION PUMP, OVERDOSES HAVE OCCURRED.
Foscarnet side effects
THE MAJOR TOXICITY OF FOSCARNET IS RENAL IMPAIRMENT (see WARNINGS section). Approximately 33% of 189 patients with AIDS and CMV retinitis who received foscarnet (60 mg/kg TID), without adequate hydration, developed significant impairment of renal function (serum creatinine ≥ 2.0 mg/dL). The incidence of renal impairment in subsequent clinical trials in which 1000 mL of normal saline or 5% dextrose solution was given with each infusion of foscarnet was 12% (34/280). Foscarnet has been associated with changes in serum electrolytes including hypocalcemia (15-30%), hypophosphatemia (8–26%) and hyperphosphatemia (6%), hypomagnesemia (15–30%), and hypokalemia (16–48%) (see WARNINGS section). The higher percentages were derived from those patients receiving hydration. Foscarnet treatment was associated with seizures in 18/189 (10%) AIDS patients in the initial five controlled studies (see WARNINGS section). Risk factors associated with seizures included impaired baseline renal function, low total serum calcium, and underlying CNS conditions predisposing the patient to seizures. The rate of seizures did not increase with duration of treatment. Three cases were associated with overdoses of foscarnet (see OVERDOSAGE section). In five controlled U.S. clinical trials the most frequently reported adverse events in patients with AIDS and CMV retinitis are shown in Table 9 . These figures…
Who shouldn’t take foscarnet
Foscarnet Sodium Injection is contraindicated in patients with clinically significant hypersensitivity to foscarnet sodium.
Foscarnet drug interactions
A possible drug interaction of FOSCARNET and intravenous pentamidine has been described. Concomitant treatment of four patients in the United Kingdom with FOSCARNET and intravenous pentamidine may have caused hypocalcemia; one patient died with severe hypocalcemia. Toxicity associated with concomitant use of aerosolized pentamidine has not been reported. Because foscarnet can reduce serum levels of ionized calcium, extreme caution is advised when used concurrently with other drugs known to influence serum calcium levels (e.g., intravenous pentamidine). Renal impairment and symptomatic hypocalcemia have been observed during concurrent treatment with foscarnet and intravenous pentamidine. Because of foscarnet's tendency to cause renal impairment, the use of foscarnet should be avoided in combination with potentially nephrotoxic drugs such as aminoglycosides, amphotericin B, cyclosporine, acyclovir, methotrexate, tacrolimus and intravenous pentamidine (see above) unless the potential benefits outweigh the risks to the patient. When diuretics are indicated, thiazides are recommended over loop diuretics because the latter inhibit renal tubular secretion, and may impair elimination of foscarnet, potentially leading to toxicity. Abnormal renal function has been observed in clinical practice during the use of foscarnet and ritonavir, or foscarnet, ritonavir, and saquinavir. (See DOSAGE and ADMINISTRATION .) Because of the risk of QT prolongation and the potential for torsades de pointes, the use of foscarnet should be avoided in combination with agents known to prolong the QT interval including Class IA (e.g., quinidine or procainamide) or Class III (e.g., dofetilide, amiodarone, sotalol) antiarrhythmic agents, phenothiazines, tricyclic antidepressants, and certain macrolides and fluoroquinolones.
Every foscarnet product we track (2)
Same active ingredient — different manufacturer, form, price and FDA recall record. That last one is what our independent score measures.
| # | Drug | Rating | Type | Form | Generic? | Pharmacy pays | |
|---|---|---|---|---|---|---|---|
| 1 | 68/100 | Prescription | Injectable | No data | — | View → | |
| 2 | Not yet rated | Prescription | Injectable | No data | — | View → |
How long foscarnet keeps
The date on a sealed pack is not the only one: some foscarnet labels start a second clock once the product is opened or mixed, as short as 24 hours.
Does foscarnet expire? The in-use limits and storage rules from its labelsWhat people report to the FDA about foscarnet
The FDA Adverse Event Reporting System (FAERS) collects reports from patients and clinicians. It holds 984 reports naming foscarnet, and the FDA flagged 97% of those reports as serious. The effects reported most often — leaving out reports about overdose, misuse or the condition being treated, which dominate the raw list for common medicines:
- acute kidney injury150 reports
- pancytopenia116 reports
- drug resistance106 reports
- cytomegalovirus infection98 reports
- nephropathy toxic92 reports
- bk virus infection80 reports
- cytomegalovirus infection reactivation80 reports
- myelosuppression80 reports
Read these as a signal, not a rate. A report does not mean foscarnet caused the effect — anyone can file one, and many describe people taking several medicines for several conditions. Crucially there is no denominator: FAERS does not record how many people took the drug, so these counts cannot be turned into “X% of patients” — a bigger number often just means a more widely used or more talked-about drug. Duplicates exist, and publicity drives reporting. For what is actually established, read the FDA label section above.
Source: openFDA drug/event (FAERS), retrieved August 25, 2026.
Related calculators
Frequently asked questions
What is foscarnet?
Foscarnet Sodium Injection is the brand name for foscarnet sodium.
What kind of drug is foscarnet?
The FDA classifies foscarnet as a pyrophosphate analog dna polymerase inhibitor. If you are checking whether it is safe to combine with something else, the class is what matters — two drugs from the same class usually should not be stacked.
Can you take foscarnet with other medicines?
It depends on the medicine. We check it against the FDA labels rather than guessing: our interaction checker searches each drug's own label for the other and quotes what it says, naming the section it came from. Run foscarnet against whatever else you take — and remember that a label not naming a drug is not the same as that combination being safe.
What brand names is foscarnet sold under?
We track 2 foscarnet-containing products in the U.S.: Foscarnet Sodium and Foscavir. They are the same active ingredient; they differ in form, manufacturer, price and FDA recall record.
What forms does foscarnet come in?
Across the brands we track, foscarnet is currently marketed as injectable and solution, per the FDA's National Drug Code Directory. Each form is dosed differently — follow the label for the exact product you were prescribed.
Is there a generic foscarnet?
Yes. Our catalog lists 1 generic foscarnet product alongside the brand versions. A generic has the same active ingredient and must meet the FDA's bioequivalence standard; it usually costs less. Ask your pharmacist which one your plan covers.
Cite this page
- APA
- pharmaranks. (2026, July 24). Foscarnet: uses, dosing, side effects & brands. https://pharmaranks.com/drugs/foscarnet
- MLA
- “Foscarnet: uses, dosing, side effects & brands.” pharmaranks, 24 July 2026, https://pharmaranks.com/drugs/foscarnet.
We summarise public FDA and NIH sources — for a clinical claim, cite the primary source we link to as well.
Sources: FDA openFDA drug label, National Drug Code Directory, and Enforcement (recall) database. This page reproduces public FDA data and is not medical advice. Dosing is set by your prescriber.
Read the full FDA label for foscarnet on DailyMed (NIH) ↗ — including its boxed warning in full.