Foscarnet
Risk Factor: CM
Class: ANTI-INFECTIVES
/ Antivirals
Contents of this page:
Fetal Risk Summary
Breast Feeding Summary
References
Questions and Answers
Fetal Risk Summary
Foscarnet has antiviral in vitro activity against all known herpesviruses, including cytomegalovirus (CMV), herpes simplex virus (HSV) types 1 and 2, human herpesvirus 6, Epstein-Barr virus, and varicella-zoster virus (1). The drug is also active in vitro against the human immunodeficiency virus (HIV) (2). It is used in patients with acquired immunodeficiency syndrome (AIDS) who have CMV retinitis or in immunocompromised patients with mucocutaneous acyclovir-resistant HSV infections.
Reproductive studies in pregnant rats with SC doses of 150 mg/kg/day, approximately one-eighth the estimated maximum daily human exposure based on area under the plasma concentration curve (AUC) comparison, caused an increase in the frequency of skeletal malformations or variations (1). Administration to pregnant rabbits with 75 mg/kg/day, approximately one-third the human dose (AUC comparison), produced similar skeletal defects or variations. In addition, dose-related genotoxic effects were seen in two in vitro tests and in one in vivo test in mice (1).
It is not known if foscarnet crosses the human placenta. The molecular weight (about 300 for the sodium salt) is low enough, however, that passage to the fetus should be expected.
Only one report describing the use of foscarnet during human pregnancy has been located. A 21-year-old woman at 18 weeks' gestation was treated with an 8-day course of IV forcarnet (total dose 43.8 g) for severe, genital acyclovir-resistant HSV type 2 (2). The patient also had a 3-year history of HIV disease that was being treated with saquinavir, lamivudine, and zidovudine. After discharge from the hospital, repeat cultures yielded HSV type 2 sensitive to acyclovir and she was treated with oral doses of this antiviral agent for the remainder of her pregnancy. She underwent a cesarean section at term to deliver a healthy, HIV-negative, female infant who was developing normally at 1 year of age. The authors, citing information received from the manufacturer, briefly reviewed two other cases of IV foscarnet therapy (2). In one case, a HIV-negative woman with acyclovir-resistant HSV encephalitis and retinitis had been treated with forcarnet (60 mg/kg IV every 8 hours) for 17 days starting at 32 weeks' gestation. She eventually delivered a healthy infant at term. The second case involved a HIV-positive patient who was treated with forcarnet (40 mg/kg IV every 8 hours) for genital HSV type 2 beginning at 29 weeks' gestation. No further information was available on this case (2).
One 1992 review suggested that the antiviral drug would be a first-line agent for pregnant HIV-positive patients with sight-threatening CMV retinitis (3). Because of the frequent occurrence of renal toxicity experienced with foscarnet in adults, however, the reviewer recommended frequent antepartum testing of the fetus and close monitoring of the amniotic fluid volume to observe for fetal renal toxicity.
Breast Feeding Summary
No reports describing the use of foscarnet during human breast feeding or during lactation have been located. Foscarnet was concentrated in the milk of lactating rats given 75 mg/kg/day SC, with milk levels 3 times higher than the peak maternal blood concentrations (1). Because excretion into human milk most likely also occurs, and because of the potentially severe toxicity that might occur in a nursing infant, women receiving foscarnet should not breast feed.
References
- Product information. Foscavir. AstraZeneca, 2001.
- Alvarez-McLeod A, Havlik J, Drew KE. Foscarnet treatment of genital infection due to acyclovir-resistant herpes simplex virus type 2 in a pregnant patient with AIDS: case report. Clin Infect Dis 1999;29:9378.
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Watts DH. Antiviral agents. Obstet Gynecol Clin North Am 1992;19:56385.
Questions and Answers
What is Foscarnet indicated for? URGENT!?, I know it can treat herpes virus with TK resistance. but what disease states?
simply put
It is indicated for patient's who have failed ganciclovir for treatment of CMV(cytimegalovirus) retinitis. In other words, when ganciclovir fails...use foscarnet!
Is it acceptable to make "niche" into a verb, as in "to niche" or "niched?"?, Example: "Phsyicians prefer to niche products according to toxicities" or "Foscarnet has been niched at the second choice drug."
See that girl over there? I niched that.
