Why is this drug prescribed?

Femara tablets contain the active ingredient letrozole, which is a type of drug called an aromatase inhibitor. It works by preventing the action of an enzyme in the body called the aromatase enzyme. The aromatase enzyme is involved in producing the female sex hormone, oestrogen, in women who have gone through the menopause. The enzyme converts the sex hormones androstenedione, and testosterone, into oestrogen. Letrozole prevents this conversion by blocking the action of the aromatase enzyme. This causes a reduction in oestrogen levels. Most breast cancers are sensitive to oestrogen, and their growth is stimulated by this hormone. By lowering the levels of oestrogen in the body, letrozole starves the breast cancer cells and stops them from growing. Letrozole is only effective in treating breast cancers that are sensitive to oestrogen. Letrozole is only effective in postmenopausal women, since before the menopause, oestrogen is mainly produced directly by the ovaries and not by the action of the aromatase enzyme.

Treatments

* Pre-operative treatment of localised hormone receptor positive breast cancer in postmenopausal women, to shrink the cancer and allow breast-conserving surgery * Immediately following surgery for hormone receptor positive early invasive breast cancer in postmenopausal women, to reduce chances of the cancer returning * Following five years standard treatment with tamoxifen for early invasive breast cancer in postmenopausal women, to reduce chances of the cancer returning * Advanced breast cancer in postmenopausal women, either as first-line treatment or where other anti-oestrogen drugs have not been effective

What side effects can this drug cause?

* Hot flushes * Disturbances of the gut such as diarrhoea, constipation, nausea, vomiting or abdominal pain * Fatigue * Hair loss * Pain in muscles or joints * Change in appetite * Headache * Dizziness * Rash, dry skin or itching * Increased sweating * Swelling of the legs and ankles due to excess fluid retention * Weight gain * Vaginal bleeding, discharge or dryness * Urinary tract infection * Tumour pain * Depression or anxiety * Memory impairment * Difficulty in breathing * Awareness of your heartbeat * Raised cholesterol levels * Difficulty sleeping