Drug interactions
Efavirenz + Erdafitinib
Severity: Major
Efavirenz and Erdafitinib: 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
Efavirenz has opposing effects on erdafitinib handling, so exposure is unpredictable. It may lower levels through CYP3A4 induction, risking loss of efficacy, or raise them via CYP2C9 effects, risking toxicity such as hyperphosphatemia and ocular events.
What this interaction means in plain words
Efavirenz and Erdafitinib 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.
Efavirenz belongs to Anti Virals; Erdafitinib belongs to Oncology.
Why it happens
Efavirenz induces CYP3A4 and has variable effects on CYP2C9, both of which metabolize erdafitinib.
What to do
Prefer an alternative antiretroviral. If coadministered, monitor serum phosphate, ocular symptoms and tumour response and adjust the erdafitinib dose accordingly.
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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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
Other interactions of Erdafitinib
Frequently asked questions
Can I take Efavirenz with Erdafitinib?
MediHelp rates the interaction as major. Efavirenz and Erdafitinib 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. Efavirenz has opposing effects on erdafitinib handling, so exposure is unpredictable. It may lower levels through CYP3A4 induction, risking loss of efficacy, or raise them via CYP2C9 effects, risking toxicity such as hyperphosphatemia and ocular events.
How serious is the interaction between Efavirenz and Erdafitinib?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Prefer an alternative antiretroviral. If coadministered, monitor serum phosphate, ocular symptoms and tumour response and adjust the erdafitinib dose accordingly.
What other medicines interact with Efavirenz?
MediHelp also lists interactions of Efavirenz with, for example, Cobimetinib, Dienogest / estradiol valerate, Dihydroergotamine intranasal. The full list is on the Efavirenz page.
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