Letrozole is available with a prescription generically and under the brand name Femara.
It is a medication that has been approved for use by the FDA for the treatment of certain types of breast cancer. It is also commonly used as “off label” for the treatment of ovulation disorders in infertility. Similar to Clomid, Letrozole stimulates the release of pituitary hormones necessary for ovulation to occur but uses a different mechanism of action. Unlike Clomid, Letrozole has a shorter half life (lifespan) in the body and has the advantage of not been associated with some of the negative effects of Clomid on the reproductive system such as poor development of the uterine lining (endometrium) and thickening of the cervical mucus.
It is important to exclude pregnancy, ovarian enlargement and ovarian cyst before each Letrozole treatment cycle.
Letrozole is orally administered, available in 2.5 mg tablets.
It is usually taken in 5 day cycles. Treatment begins with a low dose, 2.5 or 5.0 mg tablet daily for 5 days.
Ovulation usually occurs 5 to 10 days after treatment.
Intercourse or intrauterine insemination (IUI) is timed to coincide with the expected time of ovulation. Timing of ovulation can be determined with basal body temperature charting, over the counter ovulation kits and pelvic ultrasounds.
Letrozole is as effective as Clomid with similar ovulation rate (60-70%) and pregnancy rate (approximately 15% per month).
Even though earlier studies suggested a higher incidence of birth defects after treatment with Letrozole, later studies did not show any difference in the rate of birth defects between Clomid and Letrozole. Nevertheless, it is a category D drug and should not be used in Pregnancy.
Side Effects of Letrozole:
- Hot flashes
- Musculoskeletal pain (joint/bone/muscle)
- Unusual sweating
- Nausea, diarrhea, dizziness
- Trouble sleeping