Foscarnet Sodium (foscarnet sodium)
Last reviewed · Source: First Databank (FDB) drug data
Overview
Foscarnet sodium (phosphonoformic acid), an organic analog of inorganic pyrophosphate, is an antiviral agent active against herpesviruses.
Foscarnet (phosphonoformic acid), an organic analog of inorganic pyrophosphate, is an antiviral agent. The drug is commercially available as the trisodium salt. Foscarnet is structurally unrelated to other currently available antiviral agents.
Unlike nucleoside and nucleotide antivirals (e.g., acyclovir, cidofovir, ganciclovir, valganciclovir), foscarnet does not require intracellular enzyme conversion to an active metabolite.
Foscarnet acts as a viral DNA polymerase inhibitor. The mechanism of action of foscarnet against herpesviruses involves selective inhibition of the pyrophosphate binding site on virus-specific DNA polymerases at concentrations that do not affect cellular DNA polymerases.
The pharmacokinetics of foscarnet sodium have been evaluated in patients with human immunodeficiency virus (HIV) infection and acquired immunodeficiency syndrome (AIDS) receiving intermittent IV infusions of the drug for the management of cytomegalovirus (CMV) retinitis. Considerable interindividual variation in plasma concentrations of the drug has been reported. Following a single 90-mg/kg dose of IV foscarnet sodium in one study, plasma concentrations of the drug ranged from 297-1775 mcg/mL.
Foscarnet is distributed into CSF; the CSF-to-plasma ratio has been reported to be 0.2-0.7. Postmortem data indicate that foscarnet accumulates in human bones, but the extent to which this occurs has not been determined. In vitro studies indicate that foscarnet is 14-17% bound to plasma proteins.
Foscarnet is not substantially metabolized and is principally excreted unchanged in urine by glomerular filtration. Following a single IV infusion of 60 mg/kg of foscarnet sodium, the plasma half-life of the drug was 1.9 hours in adults with normal renal function (creatinine clearance greater than 80 mL/minute) and approximately 3, 13, and 25 hours in those with creatinine clearances of 50-80, 25-49, and 10-24 mL/minute, respectively. However, the terminal half-life of foscarnet determined by urinary excretion has been reported to be 87.5 hours, most likely because of slow release of the drug from bone.
USES: This medication is used to control cytomegalovirus (CMV) eye infections (CMV retinitis) in persons with AIDS. This medication is an antiviral that works by stopping the growth of viruses. Controlling CMV retinitis can help decrease the risk of blindness from the infection.
Foscarnet is sometimes combined with another antiviral drug, ganciclovir, when the CMV infection does not respond to either drug used alone for treatment. This medication is also used to treat herpes infections (HSV) that do not respond to treatment with acyclovir (acyclovir-resistant). This medication is not a cure for CMV or HSV diseases.
Generic name: foscarnet sodium
Pronunciation: (foss-KAR-net)
Reference product & biosimilars
No reference, biosimilar or interchangeable associated with this drug.
Today’s intelligence on Foscarnet Sodium
Indications
The following indications are listed for Foscarnet Sodium:
- Acyclovir-Resistant Mucocutaneous Hsv In Immunocompromised Patient
- Cmv Retinitis In Aids Patient
Also known as: Cytomegalovirus Retinitis In Aids.
Dosing
Foscarnet is commercially available as the hydrated trisodium salt (i.e., foscarnet sodium); dosage is expressed in terms of foscarnet sodium.
Foscarnet sodium is administered by slow IV infusion using a controlled-infusion device (e.g., pump). The drug should not be administered by rapid IV infusion or direct IV injection since potentially toxic plasma foscarnet concentrations may result.
Foscarnet has been administered by intravitreal injection+; however, a preparation of the drug specifically for intravitreal administration is not commercially available in the US.
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Drug interactions
There is no enhanced messaging for this drug.
There are no contraindication interactions for this drug.
There are no severe interactions for this drug.
There are no moderate interactions for this drug.
Contraindications
Foscarnet sodium is contraindicated in patients with clinically important hypersensitivity to the drug.
There are no contraindication contraindications for this drug.
There are no severe contraindications for this drug.
There are no moderate contraindications for this drug.
Adverse reactions
Adverse effects reported in 10% or more of patients receiving foscarnet include fever, nausea, anemia, diarrhea, abnormal renal function, vomiting, headache, seizures, and marrow suppression.
There are no severe adverse reactions for this drug.
There are no less severe adverse reactions for this drug.
Precautions
No enhanced messaging available.
Safety and efficacy of foscarnet sodium have not been established in pediatric patients younger than 18 years of age.
The manufacturer states that the drug should be used in children+only after careful evaluation and only when potential benefits of the drug outweigh possible risks.
Some experts recommend foscarnet as the preferred alternative for the management of CMV retinitis, acyclovir-resistant mucocutaneous HSV infections, and acyclovir-resistant varicella-zoster virus (VZV) infections in HIV-infected children+.
In animals, foscarnet is deposited in teeth and bone and such deposition is greater in those that are young and growing. Foscarnet adversely affects tooth enamel development in mice and rats; the effects of drug deposition on skeletal development have not been studied. There is evidence that foscarnet accumulates in bone in humans, but the extent to which this occurs has not been studied. Since foscarnet is deposited in human bone, it is likely that it does so to a greater degree in developing bone in children.
There are no adequate and well-controlled studies to date using foscarnet sodium in pregnant women. The drug should be used during pregnancy only when clearly needed.
Reproduction studies in female rats given subcutaneous foscarnet sodium in doses up to 75 mg/kg daily prior to and during mating, during gestation, and through 21 days postpartum caused a slight increase (less than 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 also caused an increased frequency of skeletal anomalies and variations. On the basis of estimated drug exposure (as measured by AUC), the 150- and 75-mg/kg doses were approximately one-eighth (rats) and one-third (rabbits) the estimated maximal daily human exposure. These data were inadequate to define the potential teratogenicity of foscarnet at dosages used in humans.
It is not known whether foscarnet is distributed into human milk. In lactating rats that received a dose of 75 mg/kg, the drug was distributed in maternal milk at concentrations 3 times higher than peak maternal blood concentrations.
Since there is potential for serious adverse reactions to foscarnet in nursing infants, a decision should be made to discontinue nursing or the drug, taking into consideration the importance of the drug to the woman.
Because of the risk of adverse effects in the infant and the risk of HIV transmission, HIV-infected women should not breast-feed infants.
Dosage of foscarnet sodium for geriatric patients should be selected with caution because of age-related decreases in renal function. (See Geriatric Use under Warnings/Precautions: Specific Populations, in Cautions.)
Safety and efficacy of foscarnet have not been specifically studied in geriatric patients 65 years of age or older.
Adverse effects reported in patients 65 years of age or older have been similar to those reported in younger adults.
Because geriatric patients frequently have decreased renal function and because foscarnet is substantially excreted by the kidneys, particular attention should be paid to evaluating renal function prior to and during foscarnet therapy in this age group. If evidence of renal impairment exists or develops, appropriate dosage adjustments should be made. (See Renal Impairment under Dosage and Administration: Special Populations.)
ICD codes
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Last reviewed · Source: First Databank (FDB) drug data
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