Drug interactions
Efavirenz + Nafcillin
Severity: Moderate
Efavirenz and Nafcillin: 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
Nafcillin can induce metabolizing enzymes and lower efavirenz concentrations, which may compromise viral suppression. The magnitude is not well characterized.
What this interaction means in plain words
Efavirenz and Nafcillin 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.
Why it happens
Nafcillin induces CYP3A4 and possibly CYP2B6, increasing efavirenz metabolism.
What to do
Monitor HIV viral load during and after the course. Consider an alternative antibiotic when appropriate.
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 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 Nafcillin?
MediHelp rates the interaction as moderate. Efavirenz and Nafcillin 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. Nafcillin can induce metabolizing enzymes and lower efavirenz concentrations, which may compromise viral suppression. The magnitude is not well characterized.
How serious is the interaction between Efavirenz and Nafcillin?
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 HIV viral load during and after the course. Consider an alternative antibiotic when appropriate.
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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