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Drug Interactions between Dura-Dumone and Femara

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

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Interactions between your drugs

Major

estradiol letrozole

Applies to: Dura-Dumone (estradiol / testosterone) and Femara (letrozole)

GENERALLY AVOID: Theoretically, estrogen-containing drugs may negate the pharmacologic effects of aromatase inhibitors in the treatment of hormone-dependent breast cancer. Aromatase inhibitors induce a state of estrogen deprivation in postmenopausal women by inhibiting the conversion of androgens to estrogens in adrenal and ovarian tissues, thus estrogen administration would be expected to reverse their therapeutic effects.

MANAGEMENT: Use of estrogen-containing products should be avoided during aromatase inhibitor therapy.

References

  1. "Product Information. Femara (letrozole)." Novartis Pharmaceuticals PROD (2001):
  2. "Product Information. Arimidex (anastrozole)." Astra-Zeneca Pharmaceuticals PROD (2001):
  3. "Product Information. Aromasin (exemestane)." Pharmacia and Upjohn PROD (2001):

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Drug and food interactions

Minor

estradiol food

Applies to: Dura-Dumone (estradiol / testosterone)

Coadministration with grapefruit juice may increase the bioavailability of oral estrogens. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall induced by certain compounds present in grapefruits. In a small, randomized, crossover study, the administration of ethinyl estradiol with grapefruit juice (compared to herbal tea) increased peak plasma drug concentration (Cmax) by 37% and area under the concentration-time curve (AUC) by 28%. Based on these findings, grapefruit juice is unlikely to affect the overall safety profile of ethinyl estradiol. However, as with other drug interactions involving grapefruit juice, the pharmacokinetic alterations are subject to a high degree of interpatient variability. Also, the effect on other estrogens has not been studied.

References

  1. Weber A, Jager R, Borner A, et al. "Can grapefruit juice influence ethinyl estradiol bioavailability?" Contraception 53 (1996): 41-7
  2. Schubert W, Eriksson U, Edgar B, Cullberg G, Hedner T "Flavonoids in grapefruit juice inhibit the in vitro hepatic metabolism of 17B-estradiol." Eur J Drug Metab Pharmacokinet 20 (1995): 219-24

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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.

See also

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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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