Letroz, most often referred to as Letrozole and sold as the brand name Femara, is a hormone therapy medication. Letrozole belongs to the group of drugs known as aromatase inhibitors because it inhibits the production of estrogen in post-menopausal women. Because estrogen stimulates the growth of breast cancer cells, this medication is used to treat breast cancer. As with any medication side effects may occur. However, Letrozole produceds fewer side effects than many other breast cancer treatments.
Common Side Effects
The most common side effects of Letrozole are caused as a result of reduced estrogen levels. These side effects are hot flashes and sweating, which are also the most common side effects of menopause. Hot flashes and sweating occur in about 30 percent of women taking Letrozole, according to the UK Cancer Research. Other common side effects, which occur in about 20 percent of Letrozole users, include painful joints, tiredness and fatigue.
Although these side effects may affect quality of life, their presence may actually be a positive sign. According to a study conducted at the University of London, those who experience hot flashes and joint pain within the first 3 months of treatment have an 11.4 percent less chance of experiencing recurrent cancer. This study was conducted using another aromatase inhibitor, Arimidex, but Arimidex and Letrozole have similar chemical structures.
Occasional Side Effects
Side effects including headache, dizziness, mild skin rashes and nausea occur in about 10 percent of patients on Letrozole. The nausea, although bothersome, is not medically harmful and can be controlled with anti-nausea medication. Fluid retention resulting in swollen fingers or ankles also occurs in about 10 percent of those taking Letrozole.
Possible Side Effects
Each person taking Letrozole experiences different side effects to different degrees. Some may experience a loss of appetite, indigestion or mild diarrhea. Letrozole may also increase blood cholesterol level. The increase is usually small, but blood cholesterol in people who take the drug should be monitored by a doctor throughout treatment.
Letrozole may also affect sexual function, causing vaginal dryness and a decrease in libido. Vaginal bleeding may also occur during the first few weeks of treatment, but should subside.
Other possible side effects include thinning hair, cough and breathlessness.
Osteoporosis
Osteoporesis, or the thinning of bone tissue and reduction in bone density, is one of the most damaging side effects of Letrozole. Osteoporosis is a result of the decrease in estrogen. Bones are continually renewing themselves, with osteoclasts that absorb old bone and osteoblasts that produce new bone. A lack of estrogen encourages the osteoclasts to absorb more bone, but because the osteoblasts are still producing at the same rate, more bone is lost than produced, resulting in osteoporosis. Osteoporosis leads to less dense bones which increases the risk for broken bones.
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