Foscarnet
FOSCAVIR
What it isPyrophosphate analog directly inhibiting viral DNA polymerase; resistant CMV and acyclovir-resistant HSV.
Why this oneBecause it needs no viral kinase activation, it works when kinase mutations defeat nucleoside analogs.
What limits itNephrotoxicity and severe electrolyte derangements, especially hypocalcemia, require saline hydration and close monitoring.
FDA label
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| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| CMV retinitis — induction | Immunocompromised adults, normal renal function | 90 mg/kg IV Q12H (1.5-2 h infusion) or 60 mg/kg IV Q8H (>=1 h infusion) x 2-3 wk | 2-3 wk induction per clinical response | 180 mg/kg/day; individualize for renal function |
| CMV retinitis — maintenance | Immunocompromised adults | 90 mg/kg IV QD over 2 h | 90-120 mg/kg IV QD (escalate to 120 for retinitis progression/good tolerance) | 120 mg/kg/day |
| Acyclovir-resistant mucocutaneous HSV | Immunocompromised adults, normal renal function | 40 mg/kg IV Q8H or Q12H (>=1 h infusion) | 2-3 wk or until healed | 120 mg/kg/day |
Renal Dose-adjust per CrCl (mL/min/kg) nomogram — required even with normal serum creatinine; discontinue if CrCl <0.4 mL/min/kg; not recommended on hemodialysis (no guidelines)
Hepatic Undefined
Do not exceed recommended dose, frequency, or infusion rate; all doses individualized for renal function
Instructions
- NEVER rapid or bolus IV — infusion pump required; max rate 1 mg/kg/min
- Central line: 24 mg/mL undiluted; peripheral vein: dilute to 12 mg/mL with D5W or NS; use within 24 h
- Hydrate: 750-1,000 mL NS/D5W before first infusion; then 750-1,000 mL with each 90-120 mg/kg dose, 500 mL with 40-60 mg/kg dose
- Administer only with NS or D5W; no other drug in same catheter; incompatible with calcium-containing solutions (LR, TPN), ganciclovir, many IV drugs
- Monitor CrCl at baseline, 2-3x/wk during induction, weekly during maintenance; monitor Ca, Mg, K, phosphate on same schedule
Cautions
- Nephrotoxicity — most patients have some renal function decline; hydration reduces risk
- Seizures assoc. with electrolyte/mineral changes (esp. hypocalcemia); caution in low baseline Ca, neurologic/cardiac disease, seizure-predisposing conditions
- Electrolyte disturbances: hypocalcemia, hypomagnesemia, hypokalemia, hypo-/hyperphosphatemia — supplement as needed
- Limited data if baseline SCr >2.8 mg/dL or CrCl <50 mL/min
- Accidental skin/eye contact: flush with water (local irritation/burning)
Adverse reactions
- Fever (65%), nausea (47%), anemia (33%), diarrhea (30%), vomiting, headache (26% ea)
- Abnormal renal function (27%); renal impairment ~12% even with hydration
- Seizures (10%)
- Electrolytes: hypokalemia (16-48%), hypocalcemia (15-30%), hypomagnesemia (15-30%), hypophosphatemia (8-26%), hyperphosphatemia (6%)
- Marrow suppression, granulocytopenia; injection-site pain/inflammation
Pregnancy No adequate human studies — use only if clearly needed; skeletal anomalies in animals at sub-human exposures
Lactation Undefined
⚠ BOXED WARNINGS
- Renal impairment
- Seizures related to mineral and electrolyte changes
Classes and tags
Clinical profile
Mechanism of action: Foscarnet ballicule
