Drug interactions
Cyclophosphamide + Efavirenz
Severity: Moderate
Cyclophosphamide and Efavirenz: 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 induces CYP enzymes, including CYP2B6 and CYP3A4, that activate cyclophosphamide to its 4-hydroxy active form. Induction can alter the balance between active and toxic metabolites, with unpredictable effects on efficacy and toxicity.
What this interaction means in plain words
Cyclophosphamide and Efavirenz 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.
Cyclophosphamide belongs to Oncology; Efavirenz belongs to Anti Virals.
Why it happens
Efavirenz induces CYP2B6 and CYP3A4, changing cyclophosphamide bioactivation and metabolite formation.
What to do
Monitor for changes in response and toxicity such as myelosuppression, and review the antiretroviral regimen with the HIV team if clinically significant effects occur.
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 Cyclophosphamide
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 Cyclophosphamide with Efavirenz?
MediHelp rates the interaction as moderate. Cyclophosphamide and Efavirenz 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 induces CYP enzymes, including CYP2B6 and CYP3A4, that activate cyclophosphamide to its 4-hydroxy active form. Induction can alter the balance between active and toxic metabolites, with unpredictable effects on efficacy and toxicity.
How serious is the interaction between Cyclophosphamide and Efavirenz?
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 for changes in response and toxicity such as myelosuppression, and review the antiretroviral regimen with the HIV team if clinically significant effects occur.
What other medicines interact with Cyclophosphamide?
MediHelp also lists interactions of Cyclophosphamide with, for example, Adenovirus types 4 and 7 live, Belatacept, Bendamustine. The full list is on the Cyclophosphamide page.
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