Medications like St. John's Wort, phenobarbital, carbamazepine (Tegretol, Tegretol XR, Equetro, Carbatrol), and rifampin (Rifadin) can accelerate the breakdown of conjugated estrogens, leading to low levels of absorbed drug and reduced effectiveness. Grapefruit juice and medications like erythromycin, clarithromycin (Biaxin, Biaxin XL), ketoconazole (Nizoral, Extina, Xolegel, Kuric), and ritonavir can slow down the breakdown of conjugated estrogens in the liver, leading to increased levels of estrogens and increased estrogen side effects.
What formulations of conjugated estrogens are available?
Conjugated estrogens are available as oral tablets and topical cream.
What about taking conjugated estrogens during pregnancy or while breastfeeding?
Conjugated estrogens are not recommended during pregnancy because it may cause birth defects in the unborn. Use of conjugated estrogens is not recommended in nursing mothers because conjugated estrogens enter breast milk and may have harmful effects on the newborn. Conjugated estrogens can also affect the quality and quantity of breast milk.
REFERENCE: FDA Prescribing Information.
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