Drug interactions
Efavirenz + Isoniazid
Severity: Moderate
Efavirenz and Isoniazid: 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 is metabolized by CYP2B6, with a smaller CYP3A4 contribution, and isoniazid has little effect on its exposure. Both drugs are hepatotoxic and can cause neuropsychiatric effects. The main concern is additive liver injury and CNS toxicity in patients treated for HIV and tuberculosis.
What this interaction means in plain words
Efavirenz and Isoniazid 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; Isoniazid belongs to Anti Bacterial.
Why it happens
Additive hepatotoxicity and neurotoxicity; minor effect on efavirenz metabolism is possible.
What to do
Monitor liver enzymes regularly and assess neuropsychiatric symptoms. Provide pyridoxine and stop the offending agent if significant hepatitis develops.
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 Isoniazid
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 Isoniazid?
MediHelp rates the interaction as moderate. Efavirenz and Isoniazid 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 is metabolized by CYP2B6, with a smaller CYP3A4 contribution, and isoniazid has little effect on its exposure. Both drugs are hepatotoxic and can cause neuropsychiatric effects. The main concern is additive liver injury and CNS toxicity in patients treated for HIV and tuberculosis.
How serious is the interaction between Efavirenz and Isoniazid?
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 liver enzymes regularly and assess neuropsychiatric symptoms. Provide pyridoxine and stop the offending agent if significant hepatitis develops.
What other medicines interact with Isoniazid?
MediHelp also lists interactions of Isoniazid with, for example, Bacillus calmette-guerin substrain tice, Benzhydrocodone / acetaminophen, Carbamazepine. The full list is on the Isoniazid page.
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