Drug interactions
Elvitegravir / cobicistat / emtricitabine / tenofovir df + Foscarnet
Severity: Major
Elvitegravir / cobicistat / emtricitabine / tenofovir df and Foscarnet: major interaction.
Last updated
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 is a well-known cause of acute kidney injury, and tenofovir disoproxil fumarate can also injure the proximal tubule. Cobicistat further raises serum creatinine by inhibiting tubular secretion, which can obscure true renal function changes. Together they raise the risk of clinically significant renal toxicity.
What this interaction means in plain words
Elvitegravir / cobicistat / emtricitabine / tenofovir df and Foscarnet 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, with tenofovir and foscarnet both eliminated by the kidney.
What to do
Avoid the combination where possible; if unavoidable, monitor serum creatinine, estimated clearance, phosphate and electrolytes closely and ensure hydration. Adjust foscarnet dosing to renal function and stop the tenofovir-containing regimen if renal function deteriorates.
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?
Pro+ members
Unlock the full page
Create an account and start a Pro+ trial to unlock the full management advice for Elvitegravir / cobicistat / emtricitabine / tenofovir df and Foscarnet, the additional notes, the evidence detail and the whole-prescription interaction checker.
- Full clinical management advice
- Additional notes
- Evidence detail
- Interaction checker for a whole prescription
Try Pro+ free for 7 days on the web. No card needed.
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 Elvitegravir / cobicistat / emtricitabine / tenofovir df with Foscarnet?
MediHelp rates the interaction as major. Elvitegravir / cobicistat / emtricitabine / tenofovir df and Foscarnet 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 is a well-known cause of acute kidney injury, and tenofovir disoproxil fumarate can also injure the proximal tubule. Cobicistat further raises serum creatinine by inhibiting tubular secretion, which can obscure true renal function changes. Together they raise the risk of clinically significant renal toxicity.
How serious is the interaction between Elvitegravir / cobicistat / emtricitabine / tenofovir df and Foscarnet?
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 where possible; if unavoidable, monitor serum creatinine, estimated clearance, phosphate and electrolytes closely and ensure hydration. Adjust foscarnet dosing to renal function and stop the tenofovir-containing regimen if renal function deteriorates.
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.
Full monographs, dosing and an interaction checker in the MediHelp app
Open the complete reference, check multi-drug interactions and use dosing tools in the MediHelp app.
