Foscarnet (Foscavir ® )
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Standard Dilutions [Amount of drug] [Infusion volume] [Infusion rate]
Stability / Miscellaneous
| Must adjust dose based on renal function.
DOSAGE AND ADMINISTRATION
Hydration: Hydration may reduce the risk of nephrotoxicity. It is recommended that 750 to 1000 mL of 0.9% sodium chloride injection or 5% dextrose solution should be given prior to the first infusion of foscarnet sodium to establish diuresis. With subsequent infusions, 750 to 1000 mL of hydration fluid should be given with 90 to 120 mg/kg of foscarnet sodium, and 500 mL with 40 to 60 mg/kg of foscarnet sodium. Hydration fluid may need to be decreased if clinically warranted.
After the first dose, the hydration fluid should be administered concurrently with each infusion of foscarnet sodium.
Compatibility with Other Solutions/Drugs: Other drugs and supplements can be administered to a patient receiving foscarnet sodium. However, care must be taken to ensure that foscarnet sodium is only administered with 0.9% sodium chloride injection or 5% dextrose solution and that no other drug or supplement is administered concurrently via the same catheter. Foscarnet has been reported to be chemically incompatible with 30% dextrose, amphotericin B, and solutions containing calcium such as Ringer’s lactate and TPN. Physical incompatibility with other IV drugs has also been reported including acyclovir sodium, ganciclovir, trimetrexate glucuronate, pentamidine isethionate, vancomycin, trimethoprim/sulfamethoxazole, diazepam, midazolam, digoxin, phenytoin, leucovorin, and prochlorperazine. Because of foscarnet’s chelating properties, a precipitate can potentially occur when divalent cations are administered concurrently in the same catheter.
Parenteral drug products must be inspected visually for particulate matter and discoloration prior to administration whenever the solution and container permit. Solutions that are discolored or contain particulate matter should not be used.
Accidental Exposure: Accidental skin and eye contact with foscarnet sodium solution may cause local irritation and burning sensation. If accidental contact occurs, the exposed area should be flushed with water.
Induction Treatment: The recommended initial dose of foscarnet sodium for patients with normal renal function is:
* For CMV retinitis patients, either 90 mg/kg (1.5 to 2 hour infusion) every twelve hours or 60 mg/kg (minimum one hour infusion) every eight hours over 2 to 3 weeks depending on clinical response.
*For acyclovir-resistant HSV patients, 40 mg/kg (minimum one hour infusion) either every 8 or 12 hours for 2 to 3 weeks or until healed.
An infusion pump must be used to control the rate of infusion. Adequate hydration is recommended to establish a diuresis (see Hydration for recommendation), both prior to and during treatment to minimize renal toxicity (see package insert for WARNINGS), provided there are no clinical contraindications.
Maintenance Treatment: Following induction treatment the recommended maintenance dose of foscarnet sodium for CMV retinitis is 90 mg/kg/day to 120 mg/kg/day (individualized for renal function) given as an intravenous infusion over 2 hours. Because the superiority of the 120 mg/kg/day has not been established in controlled trials, and given the likely relationship of higher plasma foscarnet levels to toxicity, it is recommended that most patients be started on maintenance treatment with a dose of 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 sodium may benefit from initiation of maintenance treatment at 120 mg/kg/day earlier in their treatment.
An infusion pump must be used to control the rate of infusion with all doses. Again, hydration to establish diuresis both prior to and during treatment is recommended to minimize renal toxicity, provided there are no clinical contraindications.
Patients who experience progression of retinitis while receiving foscarnet sodium maintenance therapy may be retreated with the induction and maintenance regimens given above or with a combination of foscarnet sodium injection and ganciclovir (see package insert for CLINICAL TRIALS section). Because of physical incompatibility, foscarnet sodium and ganciclovir must NOT be mixed.
Use in Patients with Abnormal Renal Function: Foscarnet sodium should be used with caution in patients with abnormal renal function because reduced plasma clearance of foscarnet will result in elevated plasma levels. In addition, foscarnet sodium has the potential to further impair renal function. Safety and efficacy data for patients with baseline serum creatinine levels greater than 2.8 mg/dL or measured 24 hour creatinine clearances < 50 mL/min are limited. Renal function must be monitored carefully at baseline and during induction and maintenance therapy with appropriate dose adjustments for foscarnet sodium as outlined below (see Dose Adjustment and PATIENT MONITORING below). During foscarnet sodium therapy if creatinine clearance falls below the limits of the dosing nomograms (0.4 mL/min/kg), foscarnet sodium should be discontinued, the patient hydrated, and monitored daily until resolution of renal impairment is ensured.
Dose Adjustment: Foscarnet sodium dosing must be individualized according to the patient’s renal function status. Refer to the Table below for recommended doses and adjust the dose as indicated. Even patients with serum creatinine in the normal range may require dose adjustment; therefore, the dose should be calculated at baseline and frequently thereafter.
To use this dosing guide, actual 24-hour creatinine clearance (mL/min) must be divided by body weight (kg), or the estimated clearance in mL/min/kg can be calculated from serum creatinine (mg/dL) using the following formula (modified Cockcroft and Gault equation):
*> means “greater than”; †≥ means “greater than or equal to”; ‡< means“less than”
Due to foscarnet sodium’s propensity to chelate divalent metal ions and alter levels of serum electrolytes, patients must be monitored closely for such changes. It is recommended that a schedule similar to that recommended for serum creatinine (see above) be used to monitor serum calcium, magnesium, potassium and phosphorus. Particular caution is advised in patients with decreased total serum calcium or other electrolyte levels before treatment, as well as in patients with neurologic or cardiac abnormalities, and in patients receiving other drugs known to influence serum calcium levels. Any clinically significant metabolic changes should be corrected. Also, patients who experience mild (e.g., perioral numbness or paresthesias) or severe (e.g., seizures) symptoms of electrolyte abnormalities should have serum electrolyte and mineral levels assessed as close in time to the event as possible.
Careful monitoring and appropriate management of electrolytes, calcium, magnesium and creatinine are of particular importance in patients with conditions that may predispose them to seizures (see WARNINGS at top of page).
Foscarnet sodium injection should be used only if the bottle and seal are intact, a vacuum is present, and the solution is clear and colorless.
Store at 20° to 25°C (68° to 77°F). [See USP Controlled Room Temperature]. Protect from excessive heat (above 40°C) and from freezing.
Revised: February, 2008
Source: [package insert]