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Drug Interactions between fosphenytoin and osimertinib

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

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Major

fosphenytoin osimertinib

Applies to: fosphenytoin and osimertinib

GENERALLY AVOID: Coadministration with potent inducers of CYP450 3A4 may decrease the plasma concentrations of osimertinib, which has been shown in vitro to be primarily metabolized by the isoenzyme. Reduced therapeutic efficacy of osimertinib should be anticipated. In a clinical pharmacokinetic study, the osimertinib systemic exposure (AUC) at steady state was reduced by 78% when given concomitantly with the potent CYP450 3A4 inducer rifampin (600 mg daily for 21 days). In addition, the AUC and peak plasma concentration (Cmax) of the pharmacologically active metabolite of osimertinib, AZ5104, also decreased by 82% and 78%, respectively.

MANAGEMENT: Concomitant use of osimertinib with potent CYP450 3A4 inducers should generally be avoided. However, if concomitant use is required, some authorities recommend increasing the dose of osimertinib to 160 mg daily during treatment with the potent 3A4 inducer and resumed at 80 mg daily, 3 weeks after discontinuation of the potent 3A4 inducer.

References

  1. Cerner Multum, Inc. "UK Summary of Product Characteristics."
  2. Cerner Multum, Inc. "Australian Product Information."
  3. (2015) "Product Information. Tagrisso (osimertinib)." Astra-Zeneca Pharmaceuticals

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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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