Basic Information
ID DDInter95 and DDInter2210
Interaction 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 (2001): [2] "Product Information. Arimidex (anastrozole)." Astra-Zeneca Pharmaceuticals (2001): [3] "Product Information. Aromasin (exemestane)." Pharmacia and Upjohn (2001):
Alternative for Anastrozole L02B
Darolutamide Tamoxifen Degarelix Abiraterone Flutamide Bicalutamide
Aminoglutethimide Relugolix Nilutamide Apalutamide Abarelix
More
Alternative for Estetrol G03A
Desogestrel Norgestimate Norethisterone Drospirenone Etynodiol Levonorgestrel
Etonogestrel Norgestrel Dienogest Norelgestromin Megestrol acetate Ulipristal
Potential Metabolism Interactions
Substrate-Substrate Interaction：If more than one drug is metabolized by the same CYP, it is possible that its metabolism is inhibited because of the competition between the drugs. That means, it can be useful to lower the dosage of the drugs in the drug-cocktail because they remain longer in the organism than in monotherapy.
Inhibitor-Inhibitor Interaction：Combining two or more inhibitors of one CYP, should be compensated by lowering the dosage of these drugs because the metabolism is reduced and the drugs remain longer in the organism than in monotherapy. Not adapting the dosage bears the risk of even more side effects.
Inhibitor-Substrate Interaction：Combining drugs that have inhibitory effect and are substrates of one particular CYP, should be compensated by lowering the dosage. They rest longer in the organism than in monotherapy. Not adapting the dosage bears the risk of even more side effects.