Official reprint from UpToDate®
www.uptodate.com ©2017 UpToDate, Inc. and/or its affiliates. All Rights Reserved.

Foscarnet: An overview

Martin Rodriguez, MD
Kimon C Zachary, MD
Section Editor
Martin S Hirsch, MD
Deputy Editor
Jennifer Mitty, MD, MPH


Foscarnet is principally used for the treatment of ganciclovir-resistant cytomegalovirus (CMV) infections in patients with the acquired immunodeficiency syndrome (AIDS) or in transplant recipients.

The mechanisms of action, pharmacokinetics, and adverse effects will be reviewed here. Treatment of the specific clinical syndromes can be found on the appropriate topic reviews.


Foscarnet (trisodium phosphonoformate) is a pyrophosphate analog. It binds reversibly near the pyrophosphate-binding site of DNA polymerase (or reverse transcriptase) without requiring further modification [1]. After binding, the drug blocks the cleavage of the pyrophosphate moiety from deoxynucleotide triphosphates, in turn halting DNA chain elongation. Foscarnet selectively inhibits viral polymerase; inhibition of mammalian DNA polymerase requires a 100-fold greater concentration of foscarnet than that required to block cytomegalovirus (CMV) replication [1].


Foscarnet inhibits the replication, at least in vitro, of multiple herpes family viruses, hepatitis B virus, and the human immunodeficiency virus (HIV) [1]. Clinically, foscarnet is employed almost exclusively to treat infections with cytomegalovirus (CMV) (particularly when ganciclovir cannot be used) [2] and acyclovir-resistant herpes simplex virus (HSV) and varicella zoster virus (VZV). Foscarnet has in vitro activity against human herpesvirus 6A and 6B, and has been used in a few cases [3]. Foscarnet is not used as an antiretroviral agent to treat HIV.


Resistance testing can identify mutations that help predict the activity of foscarnet [4-6]. This can be used to guide antiviral therapy, especially in patients who have failed their initial regimen.

To continue reading this article, you must log in with your personal, hospital, or group practice subscription. For more information on subscription options, click below on the option that best describes you:

Subscribers log in here

Literature review current through: Nov 2017. | This topic last updated: Jun 08, 2017.
The content on the UpToDate website is not intended nor recommended as a substitute for medical advice, diagnosis, or treatment. Always seek the advice of your own physician or other qualified health care professional regarding any medical questions or conditions. The use of this website is governed by the UpToDate Terms of Use ©2017 UpToDate, Inc.
  1. Wagstaff AJ, Bryson HM. Foscarnet. A reappraisal of its antiviral activity, pharmacokinetic properties and therapeutic use in immunocompromised patients with viral infections. Drugs 1994; 48:199.
  2. Tan BH. Cytomegalovirus Treatment. Curr Treat Options Infect Dis 2014; 6:256.
  3. Agut H, Bonnafous P, Gautheret-Dejean A. Update on infections with human herpesviruses 6A, 6B, and 7. Med Mal Infect 2017; 47:83.
  4. Le Page AK, Jager MM, Iwasenko JM, et al. Clinical aspects of cytomegalovirus antiviral resistance in solid organ transplant recipients. Clin Infect Dis 2013; 56:1018.
  5. Gregg K, Hakki M, Kaul DR. UL54 foscarnet mutation in an hematopoietic stem cell transplant recipient with cytomegalovirus disease. Transpl Infect Dis 2014; 16:320.
  6. Piret J, Boivin G. Antiviral drug resistance in herpesviruses other than cytomegalovirus. Rev Med Virol 2014; 24:186.
  7. Meyer PR, Matsuura SE, Zonarich D, et al. Relationship between 3'-azido-3'-deoxythymidine resistance and primer unblocking activity in foscarnet-resistant mutants of human immunodeficiency virus type 1 reverse transcriptase. J Virol 2003; 77:6127.
  8. Arevalo JF, Gonzalez C, Capparelli EV, et al. Intravitreous and plasma concentrations of ganciclovir and foscarnet after intravenous therapy in patients with AIDS and cytomegalovirus retinitis. J Infect Dis 1995; 172:951.
  9. Astra Arcus. Foscarnet international prescribing information. March 1993.
  10. Trifillis AL, Cui X, Drusano GL. Use of human renal proximal tubule cell cultures for studying foscarnet-induced nephrotoxicity in vitro. Antimicrob Agents Chemother 1993; 37:2496.
  11. Maurice-Estepa L, Daudon M, Katlama C, et al. Identification of crystals in kidneys of AIDS patients treated with foscarnet. Am J Kidney Dis 1998; 32:392.
  12. Goldfarb DS, Coe FL. Foscarnet crystal deposition and renal failure. Am J Kidney Dis 1998; 32:519.
  13. Philipponnet C, Michel PA, Daudon M, et al. Intravascular foscarnet crystal precipitation causing multiorgan failure. Am J Kidney Dis 2015; 65:152.
  14. Berns JS, Cohen RM, Stumacher RJ, Rudnick MR. Renal aspects of therapy for human immunodeficiency virus and associated opportunistic infections. J Am Soc Nephrol 1991; 1:1061.
  15. Deray G, Martinez F, Katlama C, et al. Foscarnet nephrotoxicity: mechanism, incidence and prevention. Am J Nephrol 1989; 9:316.
  16. Navarro JF, Quereda C, Quereda C, et al. Nephrogenic diabetes insipidus and renal tubular acidosis secondary to foscarnet therapy. Am J Kidney Dis 1996; 27:431.
  17. Farese RV Jr, Schambelan M, Hollander H, et al. Nephrogenic diabetes insipidus associated with foscarnet treatment of cytomegalovirus retinitis. Ann Intern Med 1990; 112:955.
  18. Zaman MM, Burney S, Landman D, Quale JM. Rapid development of renal insufficiency with the simultaneous administration of amphotericin B and foscarnet. Clin Infect Dis 1996; 22:378.
  19. Brady RC, Bernstein DI. Treatment of herpes simplex virus infections. Antiviral Res 2004; 61:73.
  20. Guillaume MP, Karmali R, Bergmann P, Cogan E. Unusual prolonged hypocalcemia due to foscarnet in a patient with AIDS. Clin Infect Dis 1997; 25:932.
  21. Physicians' Desk Reference, 52nd ed, Medical Economics Company, Montvale, NJ 1998.