Foscarnet

Foscarnet exerts its antiviral activity by a selective inhibition at the pyrophosphate binding site on virus-specific DNA polymerases at concentrations that do not affect cellular DNA polymerases. Foscarnet does not require activation (phosphorylation) by thymidine kinase or other kinases.

• CMV Retinitis Foscarnet sodium injection is indicated for the treatment of CMV retinitis in patients with acquired immunodeficiency syndrome (AIDS). Combination therapy with foscarnet sodium injection and ganciclovir is indicated for patients who have relapsed after monotherapy with either drug.

• Foscarnet sodium injection is contraindicated in patients with clinically significant hypersensitivity to foscarnet sodium.contraindicated

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.

Renal Impairment THE MAJOR TOXICITY OF FOSCARNET SODIUM INJECTION IS RENAL IMPAIRMENT (see ADVERSE REACTIONS section). Renal impairment is most likely to become clinically evident during the second week of induction therapy, but may occur at any time during foscarnet sodium injection treatment. Renal function should be monitored carefully during both induction and maintenance therapy (see PATIENT MONITORING section). Elevations in serum creatinine are usually, but not always, reversible following discontinuation or dose adjustment of foscarnet sodium injection. Safety and efficacy data for patients with baseline serum creatinine levels greater than 2.8 mg/dL or measured 24-hour creatinine clearances <50 mL/min are limited. SINCE FOSCARNET SODIUM INJECTION HAS THE POTENTIAL TO CAUSE RENAL IMPAIRMENT, DOSE ADJUSTMENT BASED ON SERUM CREATININE IS NECESSARY. Hydration may reduce the risk of nephrotoxicity. It is recommended that 750 to 1,000 mL of normal saline or 5% dextrose solution should be given prior to the first infusion of foscarnet sodium injection to establish diuresis. With subsequent infusions, 750 to 1,000 mL of hydration fluid should be given with 90 to 120 mg/kg of foscarnet sodium injection, and 500 mL with 40 to 60 mg/kg of foscarnet sodium injection. Hydration fluid may need to be decreased if clinically warranted. After the first dose, the hydration fluid should be administered concurrently with each infusion of foscarnet sodium injection.

THE MAJOR TOXICITY OF FOSCARNET SODIUM INJECTION IS RENAL IMPAIRMENT (see WARNINGS section). Approximately 33% of 189 patients with AIDS and CMV retinitis who received foscarnet sodium injection (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 1,000 mL of normal saline or 5% dextrose solution was given with each infusion of foscarnet sodium injection was 12% (34/280). Foscarnet sodium injection has been associated with changes in serum electrolytes including hypocalcemia (15 to 30%), hypophosphatemia (8 to 26%) and hyperphosphatemia (6%), hypomagnesemia (15 to 30%), and hypokalemia (16 to 48%) (see WARNINGS section). The higher percentages were derived from those patients receiving hydration. Foscarnet sodium injection 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 sodium injection (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 were calculated without reference to drug relationship or severity.

Pregnancy There are no adequate and well-controlled studies of foscarnet sodium injection in pregnant women. Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed. Animal Data: Foscarnet sodium injection did not adversely affect fertility and general reproductive performance in rats. The results of peri- and post-natal studies in rats were also negative. However, these studies used exposures that are inadequate to define the potential for impairment of fertility at human drug exposure levels. Daily subcutaneous doses up to 75 mg/kg administered to female rats prior to and during mating, during gestation, and 21 days post-partum caused a slight increase (< 5%) in the number of skeletal anomalies compared with the control group. Daily subcutaneous doses up to 75 mg/kg administered to rabbits and 150 mg/kg administered to rats during gestation caused an increase in the frequency of skeletal anomalies/variations. On the basis of estimated drug exposure (as measured by AUC), the 150 mg/kg dose in rats and 75 mg/kg dose in rabbits were approximately one-eighth (rat) and one-third (rabbit) the estimated maximal daily human exposure. These studies are inadequate to define the potential teratogenicity at levels to which women will be exposed.

Metabolism

The pharmacokinetics of foscarnet has been determined after administration as an intermittent intravenous infusion during induction therapy in AIDS patients with CMV retinitis. Observed plasma foscarnet concentrations in four studies (FOS-01, ACTG-015, FP48PK, FP49PK) are summarized in Table 7 : TABLE 7 Foscarnet Pharmacokinetic Characteristics* *Values expressed as mean S.D.

In controlled clinical trials performed in the United States, overdosage with foscarnet sodium injection was reported in 10 out of 189 patients. All 10 patients experienced adverse events and all except one made a complete recovery. One patient died after receiving a total daily dose of 12.5 g for three days instead of the intended 10.9 g. The patient suffered a grand mal seizure and became comatose. Three days later the patient expired with the cause of death listed as respiratory/cardiac arrest. The other nine patients received doses ranging from 1.14 times to 8 times their recommended doses with an average of 4 times their recommended doses. Overall, three patients had seizures, three patients had renal function impairment, four patients had paresthesias either in limbs or perioral, and five patients had documented electrolyte disturbances primarily involving calcium and phosphate. Overdose (up to 20 times the recommended dose) has been reported in post-marketing use of foscarnet sodium injection. Some of these post-marketing reports were relative overdoses in that the dose of foscarnet sodium injection had not been adjusted in patients with a reduced renal function.

• Sep 27, 1991NDANDA020068Clinigen Hlthcare
• Jan 29, 2021ANDAANDA212483Fresenius Kabi Usa
• Apr 21, 2021ANDAANDA213001Gland
• Jun 5, 2023ANDAANDA213807Avet Lifesciences
• Nov 29, 2023ANDAANDA213987Sciecure
• Mar 1, 2024ANDAANDA216602Amneal
• May 13, 2026ANDAANDA220068Caplin

1. 1Off Label Use85222%
2. 2Drug Ineffective61516%
3. 3Drug Resistance50113%
4. 4Cytomegalovirus Infection39010.0%
5. 5Acute Kidney Injury3178.1%
6. 6Pancytopenia2787.1%
7. 7Renal Impairment2506.4%
8. 8Pathogen Resistance2426.2%
9. 9Cytomegalovirus Infection Reactivation2325.9%
10. 10Cytomegalovirus Viraemia2245.7%
11. 11Nephropathy Toxic2215.6%
12. 12Pyrexia1864.7%
13. 13Neutropenia1844.7%
14. 14Encephalitis Cytomegalovirus1694.3%
15. 15Myelosuppression1503.8%

Recent PubMed references pinned to Foscarnet as a MeSH major topic. Citations link to pubmed.ncbi.nlm.nih.gov.

• Intravitreal foscarnet is an effective adjunct after systemic therapy failure in pediatric antiviral-resistant cytomegalovirus retinitis.
  The Journal of international medical research · 2026 · Amiri I, Shah P, Soleimani M, et al.
  PMID 41986961DOI 10.1177/03000605261436565
• A new locus of foscarnet resistance in the cytomegalovirus UL54 DNA polymerase gene among uncharacterized mutations in recent clinical trials.
  Antiviral research · 2026 · Chou S, Minyard A, Watanabe J, et al.
  PMID 41482062DOI 10.1016/j.antiviral.2025.106340
• Effect of Prophylactic Administration of Foscarnet for HHV-6 Encephalitis in Adult Single Cord Blood Transplantation.
  Transplant infectious disease : an official journal of the Transplantation Society · 2026 · Suzuki K, Kanda J, Iemura T, et al.
  PMID 41358680DOI 10.1111/tid.70147
• Recurrent corticosteroid-resistant cytomegalovirus infection complicating ulcerative colitis responding to antiviral treatment: Case report.
  International journal of clinical pharmacology and therapeutics · 2026 · Ayadi S, Ghithia N, Trad N, et al.
  PMID 41122010DOI 10.5414/CP204720
• Foscarnet Versus Ganciclovir for Severe Congenital Cytomegalovirus Infection: Short- and Long-Term Follow-Up.
  Viruses · 2025 · Nigro G, Buzzi M, Catenaro M, et al.
  PMID 40431731DOI 10.3390/v17050720
• Real-World Comparison of Maribavir to Foscarnet for the Treatment of Cytomegalovirus in Solid Organ and Hematopoietic Stem Cell Transplant Recipients.
  Viruses · 2024 · Ogawa L, Morinishi C, Multani A, et al.
  PMID 39772196DOI 10.3390/v16121889
• Association between early anti-cytomegalovirus therapy and the incidence of chronic graft-versus-host disease.
  International journal of hematology · 2025 · Miyao K, Murata M, Nishida T, et al.
  PMID 39543007DOI 10.1007/s12185-024-03871-4
• Foscarnet-induced nephropathy in a kidney transplant recipient.
  Kidney international · 2024 · Rios IP, Nguyen CHL, Misra SS, et al.
  PMID 38906646DOI 10.1016/j.kint.2024.02.017

The 10 most recently updated of 38 ClinicalTrials.gov registrations naming Foscarnet as an intervention. Registration is not evidence of efficacy or safety — reference crosswalk only.

• Trial on Efficacy and Safety of Pritelivir Tablets for Treatment of Acyclovir-resistant Mucocutaneous HSV (Herpes Simplex Virus) Infections in Immunocompromised Subjects
  Completed · Phase 3 · Interventional · 158 enrolled · AiCuris Anti-infective Cures AG
  NCT03073967updated 2026-06-12
• Letermovir Prophylaxis in Children With EBV-Positive T/NK-Cell Lymphoproliferative Disease and Refractory/Relapsed EBV-Associated Hemophagocytic Lymphohistiocytosis
  Recruiting · Interventional · 80 enrolled · Beijing Children's Hospital
  NCT07488728updated 2026-03-23
• A Study of Maribavir in Chinese Adults With Cytomegalovirus (CMV) Infections
  Recruiting · Phase 3 · Interventional · 20 enrolled · Takeda
  NCT06439342updated 2026-03-02
• Infection Prophylaxis and Management in Treating Cytomegalovirus (CMV) Infection in Patients With Hematologic Malignancies Previously Treated With Donor Stem Cell Transplant
  Active not recruiting · Observational · 153 enrolled · City of Hope Medical Center
  NCT01199562updated 2026-01-28
• Pharmacokinetics of Drugs Administered to Children
  Recruiting · Observational · 200 enrolled · Duke University
  NCT03481881updated 2026-01-07
• A Study of LIVTENCITY (Maribavir) in Adults With Cytomegalovirus (CMV) Infection After Transplantation in South Korea
  Recruiting · Observational · 168 enrolled · Takeda
  NCT06555432updated 2025-11-18
• Efficacy and Safety of Cytotect®CP, Hyperimmune Anti-CMV IVIg as CMV Prophylaxis in Patients Developing Acute Grade II-IV GVHD After Allogeneic Hematopoietic Cell Transplantation.
  Terminated · Phase 2 · Interventional · 2 enrolled · University Hospital, Lille
  NCT05370976updated 2025-09-30
• CMV-CTL for the Treatment of CMV Infection After HSCT
  Completed · Phase 4 · Interventional · 5 enrolled · Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine
  NCT03004261updated 2023-04-25
• Comparison of Foscarnet Versus Vidarabine in the Treatment of Herpes Infection in Patients With AIDS Who Have Not Had Success With Acyclovir
  Completed · Phase 3 · Interventional · 26 enrolled · National Institute of Allergy and Infectious Diseases (NIAID)
  NCT00000985updated 2021-11-04
• A Study of Foscarnet Plus Ganciclovir in the Treatment of Cytomegalovirus of the Eye in Patients With AIDS Who Have Already Been Treated With Ganciclovir
  Completed · Phase 1 · Interventional · 30 enrolled · National Institute of Allergy and Infectious Diseases (NIAID)
  NCT00000970updated 2021-11-04

Frequently asked questions

How does Foscarnet work?

Foscarnet exerts its antiviral activity by a selective inhibition at the pyrophosphate binding site on virus-specific DNA polymerases at concentrations that do not affect cellular DNA polymerases. Foscarnet does not require activation (phosphorylation) by thymidine kinase or other kinases.

What is Foscarnet used for?

According to FDA labeling, Foscarnet carries indications including: CMV Retinitis Foscarnet sodium injection is indicated for the treatment of CMV retinitis in patients with acquired immunodeficiency syndrome (AIDS). Combination therapy with foscarnet sodium injection and ganciclovir is indicated for patients who have relapsed after monotherapy with either drug.. This is a reference summary of labeled uses, not medical advice or a treatment recommendation.

What class of drug is Foscarnet?

Foscarnet is classified as Phosphonic acid derivatives, Pyrophosphate Analog DNA Polymerase Inhibitor, Chelating Activity, DNA Polymerase Inhibitors, Reverse Transcriptase Inhibitors, Decreased DNA Replication, Decreased Protein Synthesis.

What are the brand names for Foscarnet?

Foscarnet is marketed under brand names including Foscavir.

What are the contraindications for Foscarnet?

Foscarnet labeling lists contraindications including: Foscarnet sodium injection is contraindicated in patients with clinically significant hypersensitivity to foscarnet sodium.. Always consult the full prescribing information and a clinician.