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Homebreast cancerFemara vs. Clomid: Facts on Fertility & Anti-Estrogen Drugs

Femara vs. Clomid: Facts on Fertility & Anti-Estrogen Drugs

What is the difference between Femara and Clomid?

What are Femara and Clomid?

Femara (letrozole) is an oral, anti-estrogen drug that is used for treating postmenopausal women with breast cancer. The growth of some breast cancers in postmenopausal women is promoted by estrogens that circulate in the blood, and the adrenal glands are the main source of these circulating estrogens. Femara inhibits the enzyme in the adrenal glands (aromatase) that produces the estrogens, estradiol and estrone.

Clomid (clomiphene) is an oral medication used for stimulating ovulation. Clomid is prescribed to stimulate ovulation in women with ovulatory dysfunction who are not pregnant, do not have abnormal bleeding or ovarian cysts, and have normal liver function. It binds to estrogen receptors in the hypothalamus, pituitary gland, ovary, endometrium, vagina, and cervix. It causes production of hormones (gonadotropins) by the pituitary, which stimulates ovulation.

What are the side effects of Femara and Clomid?


The most common side effects with letrozole are:

Cholesterol levels may increase during letrozole therapy. Cholesterol levels should be monitored and some patients may require treatment for high cholesterol levels. Letrozole decreases bone mineral density, increasing the risk of osteoporosis and fractures.


The most common side effects of clomiphene are:

  • ovarian enlargement,
  • flushing,
  • stomach discomfort,
  • breast discomfort,
  • blurred vision,
  • nausea, and
  • vomiting.

Other important side effects include

What is the dosage of Femara vs. Clomid?


The recommended dose is 2.5 mg once daily with or without food. Patients with severe liver impairment should receive 2.5 mg every other day.


The recommended dose is 50 to 100 mg orally for 5 days. The initial dose is 50 mg which may be increased to 100 mg if there is no response. Dosage may be repeated as early as 30 days after the previous treatment.

What drugs interact with Femara and Clomid?


Tamoxifen reduces blood levels of letrozole when both drugs are administered together. However, in clinical studies the benefit of letrozole was not reduced when administered immediately after tamoxifen. Letrozole is an anti-estrogen drug. Therefore, estrogen containing products counteract the effect of letrozole.


No drug interactions are listed in the prescribing information.


The first sign of pregnancy is most often:
See Answer

Are Femara and Clomid safe to take while pregnant or breastfeeding?


Letrozole damages the fetus. It should not be taken by pregnant women. It is not known if letrozole is secreted into breast milk.


Clomiphene should not be taken by pregnant women since it does not offer any benefit to pregnant women.

It is not known whether clomiphene is excreted into breast milk. It may reduce lactation in some women.


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