Drug information of Foscarnet

Foscarnet

Drug group:

Mechanism of effect

Pyrophosphate analogue which acts as a noncompetitive inhibitor of many viral RNA and DNA polymerases as well as HIV reverse transcriptase. Similar to ganciclovir, foscarnet is a virostatic agent. Foscarnet does not require activation by thymidine kinase.

Pharmacokinetics

Peak Plasma Concentration: 589 µM (60 mg/kg q8hr), 623 µM (90 mg/kg q12hr)

Protein Bound: 14-17%

Volume of distribution: 0.41 L/kg (60 mg/kg q8hr), 0.52 L/kg (90 mg/kg q12hr)

Half-life: 4 hr (60 mg/kg q8hr); 3.3 hr (90 mg/kg q12hr)

Renal clearance: 5.6 L/hr (60 mg/kg q8hr), 6.4 L/hr (90 mg/kg q12hr)

Total body clearance: 6.2 L/hr (60 mg/kg q8hr); 7.1 L/hr (90 mg/kg q12hr)

Metabolism:Biotransformation does not occur

Excretion:Urine (≤28% as unchanged drug)

Drug indications

Herpes Simplex

-CMV Retinitis

-Herpes Simplex

Dosage

CMV Retinitis 

Induction treatment: 60 mg/kg/dose every 8 hours for 14 to 21 days or 90 mg/kg/dose every 12 hours for 14 to 21 days-CMV Retinitis

Maintenance therapy: 90 to 120 mg/kg/dose once daily; due to lower toxicity, begin with 90 mg/kg/dose once daily, may escalate to 120 mg/kg/dose once daily if lower dose tolerated or for retinitis progression (manufacturer’s labeling). Duration of maintenance therapy is ≥3 to 6 months and until lesions are inactive and until CD4 count is >100 cells/mm3 for 3 to 6 months in response to antiretroviral therapy in HIV-infected patients

Herpes simplex infection (acyclovir-resistant):

 Induction: IV: 40 mg/kg/dose every 8 to 12 hours for 14 to 21 days.

Drug contraindications

hypersensitivity to drug or its components.

Hypersensitivity

Side effects

anemia , depression , Epilepsy , kidney stone , Anxiety , Fever , Diarrhea , Headache , Nephrotic syndrome , Proteinuria , nausea , vomiting , Seizures , vertigo , confusion , renal tubular necrosis , tiredness , Leukopenia , Rash , Ventricular Arrhythmia , Decreased creatinine clearance , Fanconi syndrome

Fever , Nausea , Anemia , Vomiting , Diarrhea , Abnormal renal function/decreased CrCl, Headache , Seizures , Fatigue, Depression, Confusion, Anxiety, Dizziness, Hypoesthesia, Malaise, Rash, Electrolyte imbalance (especially potassium, calcium, magnesium, and phosphorus), Leukopenia, Neutropenia, Esophageal ulceration, renal tubular acidosis, renal tubular necrosis, and crystal-induced nephropathy, status epilepticus, ventricular arrhythmia, prolongation of QT interval, torsade de pointes, gamma GT increased, diabetes insipidus (usually nephrogenic), renal calculus, Fanconi syndrome acquired, hypercalcemia, hypernatremia, and muscle disorders including myopathy, myositis, administration site extravasation, localized edema, hypersensitivity reactions (including anaphylactic shock, urticaria and angioedema) (see WARNINGS section), gastrointestinal hemorrhage, increased lipase, glomerulonephritis, nephrotic syndrome, proteinuria

Aminoglycosides , Loop Diuretics , Pentamidine (Systemic) ,QT-prolonging Agents (Highest Risk) 

Alerts

-Renal impairment is the major toxicity; reduce nephrotoxicity risk by IV prehydration with normal saline

-Monitor serum creatinine level, and, if indicated, adjust dose according to renal impairment

-Seizures, related to alterations in plasma minerals and electrolytes, reported; mineral and electrolyte supplementation may be required

-Serious acute hypersensitivity reactions reported; if such acute reactions occur, discontinue therapy;

-Associated with prolongation of QT interval, an ECG abnormality that has been associated with torsades de pointes, reported during postmarketing surveillance. use caution in patients with history of QT prolongation, taking medications known to prolong the QT interval, patients with electrolyte disturbances, or patients who have other risk factors for QT prolongation

-Dental effects: Foscarnet is deposited in teeth and bone of young, growing animals

- May cause anemia and granulocytopenia

Points of recommendation

-Caution with renal impairment

-Do not administer by rapid or bolus IV injection; use infusion pump

-Due to sodium content of foscarnet ,avoid foscarnet use when IV infusion of large amount of sodium or water may not be tolerated , avoid foscarnet use in patients on a controlled sodium diet

-Administer only into vein with adequate blood flow to prevent tissue irritation/ulceration

Pregnancy level

C

 

Breast feeding warning

not known if excreted in breast milk, do not nurse.

Drug forms

Foscavir

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