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Drug Interactions between gefitinib and rifabutin

This report displays the potential drug interactions for the following 2 drugs:

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Interactions between your drugs

Moderate

rifabutin gefitinib

Applies to: rifabutin and gefitinib

MONITOR: Coadministration with inducers of CYP450 3A4 may decrease the plasma concentrations of gefitinib, which is primarily metabolized by the isoenzyme. When a single 500 mg dose of gefitinib was administered following pretreatment with the potent CYP450 3A4 inducer rifampin (600 mg once daily for 16 days) in healthy male volunteers, mean gefitinib systemic exposure (AUC) decreased by 83% compared to administration of gefitinib alone. The interaction has not been studied with other, less potent inducers.

MANAGEMENT: The potential for diminished pharmacologic effects of gefitinib should be considered during coadministration with CYP450 3A4 inducers. Pharmacologic response to gefitinib should be monitored more closely whenever a CYP450 3A4 inducer is added to or withdrawn from therapy, and the gefitinib dosage adjusted as necessary.

References (5)
  1. Li J, Zhao M, He P, Hidalgo M, Baker SD (2007) "Differential metabolism of gefitinib and erlotinib by human cytochrome p450 enzymes." Clin Cancer Res, 13, p. 3731-7
  2. (2023) "Product Information. Iressa (gefitinib)." Astra-Zeneca Pharmaceuticals
  3. (2022) "Product Information. Apo-Gefitinib (gefitinib)." Apotex Inc
  4. (2023) "Product Information. Iressa (gefitinib)." AstraZeneca UK Ltd
  5. (2021) "Product Information. Iressa (gefitinib)." AstraZeneca Pty Ltd

Drug and food interactions

No alcohol/food interactions were found. However, this does not necessarily mean no interactions exist. Always consult your healthcare provider.

Therapeutic duplication warnings

No warnings were found for your selected drugs.

Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.

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Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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