Foscarnet
Foscarnet is an antiviral medication used primarily to treat serious cytomegalovirus (CMV) infections in immunocompromised patients, particularly those with AIDS or organ transplants. It is also used for acyclovir-resistant herpes simplex virus infections. The drug works by selectively inhibiting virus-specific DNA polymerases without affecting cellular DNA polymerases.
Foscarnet is an IV antiviral used to treat CMV and resistant herpes infections in immunocompromised patients by inhibiting viral DNA polymerase.
This medication carries a boxed (black box) warning — the strongest type of FDA warning. Review the full prescribing information before use.
Key facts at a glance
- ATC
- J05AD01
- RxNorm
- 33562
- Generic
- Foscarnet
- Class
- atc-j05
- Brands
- Foscavir
- Availability
- rx
- Lactation
- unknown
- Routes
- —
- Forms
- injection
- Regions
- US, EU, CN, JP
- Monitoring
- —
This page is for informational purposes only.
Do not use this information to diagnose yourself or to replace a physician's advice. Always consult a qualified healthcare provider before starting, stopping, or changing any medication. If you believe you are experiencing a medical emergency, call your local emergency number immediately.
Dosage and administration
- Usual dose
- 40mg/kg every 8 hours
- Maximum
- consult physician
- Frequency
- every 8 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 40mg/kg every 8 hours
- Maximum
- consult physician
- Frequency
- every 8 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
- Usual dose
- 20-30mg/kg every 12 hours
- Maximum
- consult physician
- Frequency
- every 12 hours
- Instructions
- Follow physician instructions
- Duration limits
- as prescribed
- Monitoring
- standard
Overdose information
Special Populations
9 groupspregnancy
first trimesteravoid if possible
avoid use during pregnancy unless benefits outweigh risks
regular fetal monitoring
Use of this medication in this population requires careful consideration of risks and benefits.
pregnancy
second trimesteruse lowest effective dose
use only if clearly needed for life-threatening CMV infection
fetal growth monitoring and ultrasound assessments
Use with caution and monitor for adverse effects.
pregnancy
third trimesteruse lowest effective dose
use only for severe CMV infections when benefits outweigh risks
fetal monitoring and assessment of renal function in newborn
Use with caution and monitor for adverse effects.
lactation
breastfeedingdiscontinue breastfeeding
do not breastfeed during treatment and for 48 hours after last dose
inform patients not to breastfeed
Use of this medication in this population requires careful consideration of risks and benefits.
pediatric_age
children under 12adjust based on body surface area and renal function
use only for acyclovir-resistant HSV or severe CMV with careful monitoring
monitor renal function serum electrolytes and for signs of toxicity
Use with caution and monitor for adverse effects.
geriatric
elderly 65reduce dose based on renal function calculate creatinine clearance
monitor renal function closely and adjust dosing accordingly
regular monitoring of renal function and electrolytes
Use with caution and monitor for adverse effects.
renal_impairment
mild creatinine clearance 50 80reduce dose by 25-50%
monitor renal function before and during treatment adjust dose based on creatinine clearance
frequent serum creatinine and electrolytes monitoring
Use with caution and monitor for adverse effects.
renal_impairment
severe creatinine clearance below 30significant dose reduction required
use with extreme caution only if benefits outweigh risks; consider alternative therapy
very close monitoring of renal function and drug levels if available
Use of this medication in this population requires careful consideration of risks and benefits.
hepatic_impairment
moderate to severeno specific recommendations limited data
use with caution and monitor liver function tests
regular liver function monitoring
Use with caution and monitor for adverse effects.
Statistics and clinical data
FDA approval year
Initial FDA approval for CMV infections in immunocompromised patients
Drug class
Pyrophosphate analog antiviral agent
Common uses
Treatment of viral infections in immunocompromised patients, especially for acyclovir-resistant HSV and ganciclovir-resistant CMV
Route of administration
Administered via IV due to poor oral bioavailability
Treatment of CMV retinitis in AIDS patients, CMV infections in immunocompromised individuals, and acyclovir-resistant herpes simplex virus infections when other antivirals are ineffective or contraindicated.
Foscarnet selectively binds to the pyrophosphate binding site on virus-specific DNA polymerases, blocking viral DNA synthesis without affecting cellular DNA polymerases. Unlike some antivirals, it does not require prior activation by viral enzymes like thymidine kinase.
Administered intravenously, requiring adequate hydration and renal function monitoring. Common adverse effects include nephrotoxicity, electrolyte disturbances (particularly hypocalcemia, hypomagnesemia, hypokalemia), and injection site reactions. Contraindicated in patients with severe renal impairment. Regular monitoring of renal function and electrolytes is essential during treatment.
Contraindications
Conditions and patient states where this medication should be avoided or used with caution.
Do not use (1)
Known allergy to this medication or its components
Use caution (1)
Consult healthcare provider for benefits vs risks assessment
Official drug label
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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed July 26, 2026. · Read our editorial policy