Foscarnet Dosage

This dosage information may not include all the information needed to use Foscarnet safely and effectively. See additional information for Foscarnet.

The information at Drugs.com is not a substitute for medical advice. ALWAYS consult your doctor or pharmacist.

Usual Adult Dose for:

Usual Pediatric Dose for:

Additional dosage information:

Usual Adult Dose for CMV Retinitis

HIV/AIDS-infected patients:
Induction therapy: 90 mg/kg IV (90 to 120 minute infusion) every 12 hours or 60 mg/kg IV (minimum 1 hour infusion) every 8 hours over 2 to 3 weeks depending on clinical response
Maintenance therapy: 90 mg/kg/day to 120 mg/kg/day IV (2 hour infusion)

Comments:
-Most patients should be started on maintenance therapy at 90 mg/kg/day. Escalation to 120 mg/kg/day may be considered should early reinduction be required because of retinitis progression. Some patients who show excellent tolerance to foscarnet may benefit from initiation of maintenance treatment at 120 mg/kg/day earlier in their treatment.
-Patients who experience progression of retinitis while receiving foscarnet maintenance therapy may be retreated with the induction and maintenance regimens with a combination of foscarnet and ganciclovir.

Usual Adult Dose for Herpes Simplex - Mucocutaneous/Immunocompromised Host

Acyclovir-resistant infection:
Induction therapy: 40 mg/kg IV (minimum 1 hour infusion) every 8 or 12 hours for 2 to 3 weeks or until healed

Usual Adult Dose for Varicella-Zoster

(Not approved by FDA)

Centers for Disease Control and Prevention (CDC) recommendations:
Acyclovir-resistant infection in HIV-infected patients: 90 mg/kg IV (90 to 120 minute infusion) every 12 hours

Comments: Recommended as alternative therapy

Usual Pediatric Dose for CMV Retinitis

(Not approved by FDA)

CDC recommendations:
Induction therapy:
HIV-exposed and HIV-infected infants and children: 60 mg/kg IV (minimum 2 hour infusion) every 8 hours for 2 to 3 weeks
HIV/AIDS-infected adolescents: 90 mg/kg IV (90 to 120 minute infusion) every 12 hours or 60 mg/kg IV (minimum 1 hour infusion) every 8 hours for 2 to 3 weeks

Maintenance therapy:
HIV-exposed and HIV-infected infants and children, HIV/AIDS-infected adolescents: 90 to 120 mg/kg IV (minimum 2 hour infusion) once a day

Comments:
-Most patients should be started on maintenance therapy at 90 mg/kg/day. Escalation to 120 mg/kg/day may be considered should early reinduction be required because of retinitis progression. Some patients who show excellent tolerance to foscarnet may benefit from initiation of maintenance treatment at 120 mg/kg/day earlier in their treatment.
-Patients who experience progression of retinitis while receiving foscarnet maintenance therapy may be retreated with the induction and maintenance regimens with a combination of foscarnet and ganciclovir.
-Recommended as alternative therapy

Usual Pediatric Dose for Herpes Simplex - Mucocutaneous/Immunocompromised Host

(Not approved by FDA)

CDC recommendations for acyclovir-resistant infection:
HIV-exposed and HIV-infected infants and children: 40 mg/kg IV (minimum 2 hour infusion) 3 times a day or 60 mg/kg IV (minimum 2 hour infusion) 2 times a day
HIV-infected adolescents: 40 mg/kg IV (minimum 1 hour infusion) every 8 or 12 hours until clinical response

Comments:
-Recommended as alternative therapy in infants and children
-Recommended as preferred therapy in adolescents

Usual Pediatric Dose for Varicella-Zoster

(Not approved by FDA)

CDC recommendations:
HIV-exposed and HIV-infected infants and children not responding to acyclovir: 40 to 60 mg/kg IV (minimum 2 hour infusion) 3 times a day for 7 to 10 days
Acyclovir-resistant infection in HIV-infected adolescents: 90 mg/kg IV (90 to 120 minute infusion) every 12 hours

Comments: Recommended as alternative therapy

Renal Dose Adjustments

Renal dose adjustments are based on actual 24-hour CrCl (mL/min) divided by body weight (kg) or the estimated CrCl in mL/min/kg calculated according to a modified Cockcroft-Gault formula.

CrCl greater than 1.4 mL/min/kg:
CMV Retinitis Induction: 60 mg/kg IV every 8 hours or 90 mg/kg IV every 12 hours
CMV Retinitis Maintenance: 90 mg/kg or 120 mg/kg IV every 24 hours
HSV induction: 40 mg/kg IV every 8 or 12 hours

CrCl greater than 1 to 1.4 mL/min/kg:
CMV Retinitis Induction: 45 mg/kg IV every 8 hours or 70 mg/kg IV every 12 hours
CMV Retinitis Maintenance: 70 mg/kg or 90 mg/kg IV every 24 hours
HSV induction: 30 mg/kg IV every 8 or 12 hours

CrCl greater than 0.8 to 1 mL/min/kg:
CMV Retinitis Induction: 50 mg/kg IV every 12 hours
CMV Retinitis Maintenance: 50 mg/kg or 65 mg/kg IV every 24 hours
HSV induction: 20 mg/kg or 35 mg/kg IV every 12 hours

CrCl greater than 0.6 to 0.8 mL/min/kg:
CMV Retinitis Induction: 40 mg/kg IV every 12 hours or 80 mg/kg IV every 24 hours
CMV Retinitis Maintenance: 80 mg/kg or 105 mg/kg IV every 48 hours
HSV induction: 35 mg/kg IV every 24 hours or 25 mg/kg IV every 12 hours

CrCl greater than 0.5 to 0.6 mL/min/kg:
CMV Retinitis Induction: 60 mg/kg IV every 24 hours
CMV Retinitis Maintenance: 60 mg/kg or 80 mg/kg IV every 48 hours
HSV induction: 25 mg/kg or 40 mg/kg IV every 24 hours

CrCl greater than 0.4 to 0.5 mL/min/kg:
CMV Retinitis Induction: 50 mg/kg IV every 24 hours
CMV Retinitis Maintenance: 50 mg/kg or 65 mg/kg IV every 48 hours
HSV induction: 20 mg/kg or 35 mg/kg IV every 24 hours

CrCl less than 0.4 mL/min/kg: Not recommended.

Liver Dose Adjustments

Data not available

Precautions

Foscarnet should not be administered by rapid or bolus IV injection. The toxicity of foscarnet may be increased as a result of excessive plasma levels. Care should be taken to avoid unintentional overdose by carefully controlling the rate of infusion. Therefore, an infusion pump must be used. In spite of the use of an infusion pump, overdoses have occurred. Hydration to establish diuresis both prior to and during treatment is recommended to minimize renal toxicity, provided there are no clinical contraindications.

To avoid local irritation, foscarnet solutions must be infused into veins with sufficient blood flow to allow rapid dilution and distribution. Vulvovaginal and penile epithelium ulcerations have been reported, and may be due to the presence of foscarnet in the urine. Adequate hydration and good personal hygiene are recommended to minimize occurrence.

Serum electrolyte abnormalities, including hypocalcemia, decreased ionized serum calcium (which may not be reflected in total serum calcium), hypophosphatemia, hyperphosphatemia, hypomagnesemia, and hypokalemia have been associated with foscarnet treatment. The manufacturer recommends monitoring electrolytes at baseline, 2 to 3 times per week during induction therapy, and at least every 1 to 2 weeks during maintenance therapy. Patients should be monitored for and advised to report possible symptoms of low ionized calcium, including perioral tingling, extremity numbness, and paresthesias. Clinicians should be prepared to treat electrolyte abnormalities, tetany, seizures, and cardiac disturbances.

Foscarnet commonly causes nephrotoxicity, thus patients receiving the drug should be monitored closely. To reduce risk of nephrotoxicity, CrCl (mL/min/kg) should be calculated even if serum creatinine is within normal limits, and doses should be adjusted accordingly. Serum creatinine should be monitored at baseline, 2 to 3 times per week during induction therapy, and at least every 1 to 2 weeks during maintenance therapy. Safety and efficacy data are limited in patients with baseline serum creatinine levels greater than 2.8 mg/dL or measured 24-hour CrCl less than 50 mL/min. Adequate hydration is recommended to decrease the incidence of renal toxicity. Dosage reductions are recommended for renally impaired patients. Caution is recommended in elderly patients who may have decreased renal function. Concomitant administration of other nephrotoxic drugs should be avoided.

Safety and effectiveness have not been established in pediatric patients (less than 18 years of age). Foscarnet is deposited in bones and teeth, with greater deposition occurring in young and growing animals. It has adversely affected development of tooth enamel in rodents. Foscarnet should only be administered to pediatric patients if the potential benefit outweighs the risks.

Dialysis

CrCl less than 0.4 mL/min/kg: Not recommended.

Other Comments

The infusion rate must not exceed 1 mg/kg/min.

Foscarnet is administered by controlled IV infusion, either by using a central venous line or by using a peripheral vein. The standard 24 mg/mL solution may be used with or without dilution when using a central venous catheter for infusion. When a peripheral vein catheter is used, the 24 mg/mL solution must be diluted to 12 mg/mL with D5W or NS prior to administration to avoid local irritation of peripheral veins.

Patients should be advised that foscarnet is not a cure for CMV retinitis or mucocutaneous herpes simplex infections.

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