Drug Groups

approved

Description

An antiviral agent used in the treatment of cytomegalovirus retinitis. Foscarnet also shows activity against human herpesviruses and HIV. [PubChem]

Indication

For the treatment of CMV retinitis in patients with acquired immunodeficiency syndrome (AIDS) and for treatment of acyclovir-resistant mucocutaneous HSV infections in immunocompromised patients.

Pharmacology

Foscarnet is an organic analogue of inorganic pyrophosphate that inhibits replication of herpes viruses in vitro including cytomegalovirus (CMV) and herpes simplex virus types 1 and 2 (HSV-1 and HSV-2). Foscarnet does not require activation (phosphorylation) by thymidine kinase or other kinases and therefore is active in vitro against HSV TK deficient mutants and CMV UL97 mutants. Thus, HSV strains resistant to acyclovir or CMV strains resistant to ganciclovir may be sensitive to foscarnet. However, acyclovir or ganciclovir resistant mutants with alterations in the viral DNA polymerase may be resistant to foscarnet and may not respond to therapy with foscarnet. The combination of foscarnet and ganciclovir has been shown to have enhanced activity in vitro.

Toxicity

Oral, rat LD₅₀: >2,000 mg/kg. Signs of overdose include renal impairment.

Affected Organisms

Biotransformation

Not metabolized.

Absorption

Poorly absorbed after oral administration (bioavailability from 12 to 22%).

Half Life

3.3-6.8 hours

Protein Binding

14-17%

Clearance

* 2.13 +/- 0.71 mL/min/kg [patients had normal renal function (CrCl > 80 mL/min]
* 68 +/- 8 mL/min/kg [CrCl was 50-80 mL/min]
* 34 +/- 9 mL/min/kg [CrCl was 25-49 mL/min]
* 20 +/- 4 mL/min/kg [CrCl was 10 - 24 mL/min]

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