Foscarnet

DEA Class; Rx

Common Brand Names; Foscavir, Phosphonoformic acid

• Antivirals, CMV; 
• Antivirals, Other

Antiviral agent; organic analog of inorganic pyrophosphate; not associated with myelosuppression; does not require phosphorylation for activation; used in CMV, herpes simplex, and varicella-zoster.

Hypersensitivity

• Fever (65%)
• Nausea (47%)
• Anemia (33%)
• Vomiting (33%)
• Diarrhea (30%)
• Abnormal renal function/decreased CrCl (27%)
• Headache (26%)
• Seizures (10%)
• Fatigue
• Depression
• Confusion
• Anxiety
• Dizziness
• Hypoesthesia
• Malaise
• Rash
• Electrolyte imbalance (especially potassium, calcium, magnesium, and phosphorus)
• Leukopenia
• Neutropenia

Caution with renal impairment

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

May be associated with changes in serum electrolytes changes including hypocalcemia, hypo- or hyperphosphatemia, hypomagnesemia, or hypokalemia

Serious acute hypersensitivity reactions (e.g., anaphylactic shock, urticaria, angioedema) reported; if such acute reactions occur, discontinue therapy; and institute appropriate medical therapy immediately

Cases of status epilepticus reported; several cases of seizures associated with death; electrolyte abnormalities may increase risk of seizures

Associated with prolongation of QT interval, an ECG abnormality that has been associated with torsades de pointes, reported during postmarketing surveillance; has occurred with confounding risk factors such as underlying cardiac disease, electrolyte abnormalities and other concomitant medications; 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; electrocardiograms (ECGs) and measurement of electrolytes should be obtained prior to treatment initiation and periodically during treatment

Due to sodium content of foscarnet (240 micromoles (5.5 mg) of sodium per mL); avoid foscarnet use when IV infusion of large amount of sodium or water may not be tolerated (e.g. in patients with cardiomyopathy); avoid foscarnet use in patients on a controlled sodium diet

Pregnancy Category: C

Lactation: not known if excreted in breast milk, do not nurse