Letrozole lowers estrogen levels in postmenopausal women, which may slow the growth of certain types of breast tumors that need estrogen to grow in the body.

Letrozole is used to treat breast cancer in postmenopausal women. It is often given to women who have been taking tamoxifen (Nolvadex, Soltamox) for 5 years.

Letrozole can harm an unborn baby or cause birth defects. Do not use if you are pregnant. You should not use Letrozole if you are allergic to letrozole, or if you have not gone completely through menopause.

Side Effects

Less serious Femara side effects may include:

  • Dizziness, drowsiness, weakness, tired feeling
  • Hot flashes, warmth in your face or chest
  • Flushing (warmth, redness, or tingly feeling)
  • Headache
  • Nausea, constipation
  • Bone pain, muscle or joint pain
  • Numbness, tingling, weakness, or stiffness in your hand or fingers
  • Pain in your hand that spreads to your arm, wrist, forearm, or shoulder
  • Night sweats