Ethinyl Estradiol; Norethindrone with Fosaprepitant Interaction Details
Medical Content Editor Dr. Brian Staiger, PharmD
Last updated
Nov 12, 2023
Interaction Effect
Reduced efficacy of contraceptives
Interaction Summary
Concomitant use of aprepitant or fosaprepitant with hormonal contraceptives may result in decreased contraceptive efficacy. Studies have demonstrated a significant decrease in the AUC and minimum concentration of ethinyl estradiol and norethindrone with concomitant administration. Patients should be advised to use an alternative or back-up method of contraception during therapy and for 1 month after the last dose of fosaprepitant or oral aprepitant.
Severity
Major
Onset
Delayed
Evidence
Theoretical
How To Manage Interaction
Due to the potential for reduced efficacy of hormonal contraceptives in patients receiving aprepitant or fosaprepitant, advise patients to use effective alternative or back-up methods of contraception during treatment and for 1 month after the last dose of fosaprepitant or oral aprepitant.
Mechanism Of Interaction
Unknown
Literature Reports
A) When oral aprepitant 100 mg was given once daily for 14 days with an oral contraceptive containing ethinyl estradiol 35 mcg and norethindrone 1 mg, the ethinyl estradiol AUC decreased by 43%, and the norethindrone AUC decreased by 8%. In a separate study, a daily dose of a combination contraceptive containing ethinyl estradiol and norethindrone was administered for 21 days. On day 8, oral aprepitant 125 mg, intravenous ondansetron 32 mg, and oral dexAMETHasone 12 mg were administered. On days 9 and 10, oral aprepitant 80 mg/day and dexAMETHasone 8 mg/day were given. On day 11, oral dexAMETHasone 8 mg was administered alone. The AUC of ethinyl estradiol decreased 19% and there was no change in the norethindrone AUC on day 10. The minimum concentration of ethinyl estradiol decreased as much as 64% and norethindrone decreased up to 60% during days 9 through 21 .
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Definitions
Severity Categories
Contraindicated
These drugs, generally, should not be used together simultaneously due to the high risk of severe adverse effects. Combining these medications can lead to dangerous health outcomes and should be strictly avoided unless otherwise instructed by your provider.
Major
This interaction could result in very serious and potentially life-threatening consequences. If you are taking this drug combination, it is very important to be under close medical supervision to minimize severe side effects and ensure your safety. It may be necessary to change a medication or dosage to prevent harm.
Moderate
This interaction has the potential to worsen your medical condition or alter the effectiveness of your treatment. It's important that you are monitored closely and you potentially may need to make adjustments in your treatment plan or drug dosage to maintain optimal health.
Minor
While this interaction is unlikely to cause significant problems, it could intensify side effects or reduce the effectiveness of one or both medications. Monitoring for changes in symptoms and your condition is recommended, and adjustments may be made if needed to manage any increased or more pronounced side effects.
Onset
Rapid: Onset of drug interaction typically occurs within 24 hours of co-administration.
Delayed: Onset of drug interaction typically occurs more than 24 hours after co-administration.
Evidence
Level of documentation of the interaction.
Established: The interaction is documented and substantiated in peer-reviewed medical literature.
Theoretical: This interaction is not fully supported by current medical evidence or well-documented sources, but it is based on known drug mechanisms, drug effects, and other relevant information.
How To Manage The Interaction
Provides a detailed discussion on how patients and clinicians can approach the identified drug interaction as well as offers guidance on what to expect and strategies to potentially mitigate the effects of the interaction. This may include recommendations on adjusting medication dosages, altering the timing of drug administration, or closely monitoring for specific symptoms.
It's important to note that all medical situations are unique, and management approaches should be tailored to individual circumstances. Patients should always consult their healthcare provider for personalized advice and guidance on managing drug interactions effectively.
Mechanism Of Interaction
The theorized or clinically determined reason (i.e., mechanism) why the drug-drug interaction occurs.
Disclaimer: The information provided on this page is for informational purposes only and should not be considered medical advice. Always consult with a qualified healthcare professional regarding your specific circumstances and medical conditions.
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