Drug interactions
Gefitinib + Isoniazid
Severity: Moderate
Gefitinib 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
Gefitinib is metabolized mainly by CYP3A4, and inhibitors can increase its concentrations and the risk of diarrhea, rash and hepatotoxicity. Isoniazid and gefitinib are each associated with liver injury, so additive hepatotoxicity is also a concern.
What this interaction means in plain words
Gefitinib 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.
Gefitinib belongs to Oncology; Isoniazid belongs to Anti Bacterial.
Why it happens
Isoniazid inhibits CYP3A4, reducing gefitinib clearance, and both drugs have hepatotoxic potential.
What to do
Monitor liver function tests regularly and watch for gefitinib adverse effects such as severe diarrhea and skin reactions. Interrupt gefitinib if significant toxicity 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 Gefitinib
Frequently asked questions
Can I take Gefitinib with Isoniazid?
MediHelp rates the interaction as moderate. Gefitinib 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. Gefitinib is metabolized mainly by CYP3A4, and inhibitors can increase its concentrations and the risk of diarrhea, rash and hepatotoxicity. Isoniazid and gefitinib are each associated with liver injury, so additive hepatotoxicity is also a concern.
How serious is the interaction between Gefitinib 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 function tests regularly and watch for gefitinib adverse effects such as severe diarrhea and skin reactions. Interrupt gefitinib if significant toxicity 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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