Drug interactions
Efavirenz + Ondansetron
Severity: Moderate
Efavirenz and Ondansetron: 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
Both drugs can prolong the QT interval, which may increase arrhythmia risk when they are used together. Efavirenz may also lower ondansetron levels through enzyme induction.
What this interaction means in plain words
Efavirenz and Ondansetron 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; Ondansetron belongs to Gastrointestinal Tract.
Why it happens
Additive QT prolongation; efavirenz induces CYP3A4 and may reduce ondansetron exposure.
What to do
Correct electrolytes and consider an ECG in patients with cardiac risk factors. Monitor for reduced antiemetic effect.
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 Ondansetron
- Apomorphine + Ondansetron Contraindicated
- Ondansetron + Thioridazine Contraindicated
- Ondansetron + Vandetanib Contraindicated
- Adagrasib + Ondansetron Major
- Amiodarone + Ondansetron Major
- Amisulpride + Ondansetron 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 Ondansetron?
MediHelp rates the interaction as moderate. Efavirenz and Ondansetron 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. Both drugs can prolong the QT interval, which may increase arrhythmia risk when they are used together. Efavirenz may also lower ondansetron levels through enzyme induction.
How serious is the interaction between Efavirenz and Ondansetron?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Correct electrolytes and consider an ECG in patients with cardiac risk factors. Monitor for reduced antiemetic effect.
What other medicines interact with Ondansetron?
MediHelp also lists interactions of Ondansetron with, for example, Apomorphine, Thioridazine, Vandetanib. The full list is on the Ondansetron page.
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