Drug interactions
Efavirenz + Foscarnet
Severity: Moderate
Efavirenz and Foscarnet: moderate 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
Efavirenz can prolong the QT interval, particularly at higher concentrations, and foscarnet electrolyte disturbances can increase arrhythmia risk. The combination may predispose to torsades de pointes.
What this interaction means in plain words
Efavirenz and Foscarnet can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Efavirenz belongs to Anti Virals; Foscarnet belongs to Anti Virals.
Why it happens
Additive QT prolongation with foscarnet-related electrolyte depletion.
What to do
Monitor ECG and electrolytes, and correct calcium, potassium and magnesium during foscarnet therapy.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Foscarnet
- Cidofovir + Foscarnet Contraindicated
- Foscarnet + Pimozide Contraindicated
- Foscarnet + Thioridazine Contraindicated
- Foscarnet + Vandetanib Contraindicated
- Adagrasib + Foscarnet Major
- Adefovir + Foscarnet Major
Other interactions of Efavirenz
- Cobimetinib + Efavirenz Contraindicated
- Dienogest / estradiol valerate + Efavirenz Contraindicated
- Dihydroergotamine intranasal + Efavirenz Contraindicated
- Dihydroergotamine + Efavirenz Contraindicated
- Doravirine + Efavirenz Contraindicated
- Efavirenz + Elbasvir / grazoprevir Contraindicated
Frequently asked questions
Can I take Efavirenz with Foscarnet?
MediHelp rates the interaction as moderate. Efavirenz and Foscarnet can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Efavirenz can prolong the QT interval, particularly at higher concentrations, and foscarnet electrolyte disturbances can increase arrhythmia risk. The combination may predispose to torsades de pointes.
How serious is the interaction between Efavirenz and Foscarnet?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor ECG and electrolytes, and correct calcium, potassium and magnesium during foscarnet therapy.
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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