Drug interactions
Erythromycin base + Isoniazid
Severity: Minor
Erythromycin base and Isoniazid: minor 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
Isoniazid may inhibit CYP3A4 and modestly increase erythromycin exposure, which is itself a CYP3A4 substrate. Higher levels may increase gastrointestinal effects, hepatotoxicity and QT prolongation.
What this interaction means in plain words
Erythromycin base and Isoniazid have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised.
Why it happens
Isoniazid weakly inhibits CYP3A4, reducing erythromycin metabolism.
What to do
No routine adjustment is needed, but monitor liver function and consider ECG if other QT-prolonging drugs are used.
What to ask your pharmacist
- Is there anything I should notice while taking both?
- Do I need to tell my doctor at the next visit?
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Other interactions of Isoniazid
Frequently asked questions
Can I take Erythromycin base with Isoniazid?
MediHelp rates the interaction as minor. Erythromycin base and Isoniazid have a small, usually unimportant interaction. Most people can take both; the pharmacist may still mention it so that any unexpected effect is recognised. Isoniazid may inhibit CYP3A4 and modestly increase erythromycin exposure, which is itself a CYP3A4 substrate. Higher levels may increase gastrointestinal effects, hepatotoxicity and QT prolongation.
How serious is the interaction between Erythromycin base and Isoniazid?
MediHelp rates it minor, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: No routine adjustment is needed, but monitor liver function and consider ECG if other QT-prolonging drugs are used.
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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