Drug interactions
Foscarnet + Tenofovir disoproxil
Severity: Major
Foscarnet and Tenofovir disoproxil: major interaction.
Last updated Sources: UK SmPC
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Foscarnet commonly causes renal impairment and electrolyte disturbances, and tenofovir can add to tubular injury. Concurrent use raises the risk of acute kidney injury, and reduced renal function increases tenofovir exposure.
What this interaction means in plain words
Foscarnet and Tenofovir disoproxil can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Why it happens
Additive nephrotoxicity with reduced renal clearance of tenofovir.
What to do
Avoid concurrent use where possible and consider a non-tenofovir antiretroviral during foscarnet therapy. If combined, monitor creatinine, calcium, magnesium, phosphate and potassium frequently.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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References
Other interactions of Foscarnet
- Cidofovir + Foscarnet Contraindicated
- Foscarnet + Pimozide Contraindicated
- Foscarnet + Thioridazine Contraindicated
- Foscarnet + Vandetanib Contraindicated
- Adagrasib + Foscarnet Major
- Adefovir + Foscarnet Major
Frequently asked questions
Can I take Foscarnet with Tenofovir disoproxil?
MediHelp rates the interaction as major. Foscarnet and Tenofovir disoproxil can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Foscarnet commonly causes renal impairment and electrolyte disturbances, and tenofovir can add to tubular injury. Concurrent use raises the risk of acute kidney injury, and reduced renal function increases tenofovir exposure.
How serious is the interaction between Foscarnet and Tenofovir disoproxil?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid concurrent use where possible and consider a non-tenofovir antiretroviral during foscarnet therapy. If combined, monitor creatinine, calcium, magnesium, phosphate and potassium frequently.
What other medicines interact with Foscarnet?
MediHelp also lists interactions of Foscarnet with, for example, Cidofovir, Pimozide, Thioridazine. The full list is on the Foscarnet page.
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