Drug interactions
Foscarnet + Tenofovir df
Severity: Major
Foscarnet and Tenofovir df: major interaction.
Last updated Sources: US FDA label
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
Both foscarnet and tenofovir disoproxil fumarate can injure the proximal renal tubule. Combined use increases the risk of acute kidney injury and electrolyte problems such as hypophosphatemia.
What this interaction means in plain words
Foscarnet and Tenofovir df 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 affecting renal tubular cells.
What to do
Avoid the combination if possible, otherwise monitor creatinine, phosphate and electrolytes closely and maintain hydration. Adjust doses to renal function and stop tenofovir if renal function worsens.
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 df?
MediHelp rates the interaction as major. Foscarnet and Tenofovir df 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. Both foscarnet and tenofovir disoproxil fumarate can injure the proximal renal tubule. Combined use increases the risk of acute kidney injury and electrolyte problems such as hypophosphatemia.
How serious is the interaction between Foscarnet and Tenofovir df?
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 the combination if possible, otherwise monitor creatinine, phosphate and electrolytes closely and maintain hydration. Adjust doses to renal function and stop tenofovir if renal function worsens.
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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