Femara Review Article
Femara (generic name letrozole) is a non-steroidal aromatase inhibitor that has been used for the adjuvant treatment of hormonally-responsive breast cancer. It works by reducing the total amount of estrogen produced primarily in the body which helps to starve cancer cells by depriving them of estrogen. The related agent to femara is anastrazole. It has also been used to treat endometriosis. Femara pcos has been use off label for ovarian stimulation by fertility doctors. The recommended dosage of femara is 2.5 mg tablet a day or as prescribed by doctor. Generally it is taken with or without food. Brand-name Femara is manufactured by Novartis Pharmaceuticals. However, the medication is also available in generic form.
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Femara (letrozole) is a non-steroidal aromatase inhibitor, which is used orally for adjuvant treatment of hormone receptor positive or hormone receptor unknown breast cancer in postmenopausal female. Femara treats advanced breast cancer followed by surgery. It inhibits production of oestrogen in body by inhibiting aromatase, an enzyme essential for biosynthesis of oestrogen. It has contraindication in pre-menopausal female, hence it is only effective in postmenopausal. Long-term use can lead to hypoestrogenism and osteoporosis.
Femara contains 2.5 mg of letrozole. It is an aromatase inhibitor. Aromatase is an enzyme that can aromatise androgen to produce oestrogen. Oestrogen has an important role in sexual development. Aromatase inhibition can prevent further growth of cancerous cells in breast by not producing oestrogen. It is established by research that in about 80% of breast cancer cases the cancer relies on oestrogen supply to grow. Hence, suppression of oestrogen supply to those cells can starve the cancer cells to reduce in number.
Oestrogen is present in both male and female body but at a significantly higher level in females. They are responsible for the growth of the breast, thickening of endometrial wall, and regulation of menstrual cycle in a female body. Other than the functions of the reproductive system, it also helps in bone formation, accelerates metabolism, helps in blood coagulation, promotes lung function, regulates fat level, and balances fluid level in human body.
Oestrogen is therefore used to treat postmenopausal syndrome, osteoporosis, and growth retardation of a few types.
Breast Cancer Statistics:
It is said that breast cancer risk in a woman is 1 in 8, which means 12% women are at risk for developing breast cancer. Breast cancer has the second highest percentage (22% approximately) of occurrence within all the types of cancer worldwide. In the year 2008, 458,503 females and in 2010, 425,000 females died only from breast cancer. About 70% of breast cancer cases are hormone receptive, which can be helped with Femara.
Letrozole is a highly selective aromatase inhibitor. Aromatase catalyzes the last step in oestrogen biosynthesis. This makes it an attractive target for selective inhibition. Letrozole prevents aromatase by competitive and reversible binding to the heme of its cytochrome P450 unit. The cytochrome P450 protein catalyzes many reactions involved in drug metabolism. These are also helpful in synthesis of steroids, cholesterols, and other lipids found in human body. P450 is found in endoplasmic reticulum of the cell which functions by simultaneous elimination of the methyl group as formate and aromatization of the A-ring following three successive hydroxylations of the 19-methyl group in androgen.
Letrozole is only effective in postmenopausal female for preventing breast cancer. Oestrogen is produced primarily in developing follicles of the ovaries, corpus luteum, and in the placenta. Secondary sources are liver, adrenal glands, and breast. In postmenopausal female the secondary sources such as breasts serve as primary source. Hence, in pre-menopausal female, ovary being the primary source of oestrogen, no effect of letrozole treatment is seen.
Dosage: Though it is varied in individual protocols, usually 2.5 mg one tablet a day oral intake is advised.
Use of Letrozole:
Other than treating hormone receptor positive breast cancer in post-menopausal female it has a few off-label uses as well. It is used in pre-treatment for termination of pregnancy in combination with some other drugs. Athletes and bodybuilders use it, in order to reduce the side effects of anabolic steroid intake. It is used to treat endometriosis as oestrogen has great effect on growth of endometrial cells. It has been used in combination with growth hormone in children and adolescents with growth retardation. In a few cases, letrozole has shown significant effectiveness in promoting spermatogenesis in the patients suffering from non-obstructive azoospermia.
The following side effects can be seen with long-term or short-term use of letrozole.
1. As letrozole prevents synthesis of oestrogen, long-term use of letrozole can lead to hypoestrogenism. Symptoms of hypoestrogenism include hot flashes, vaginal dryness, urinary stress incontinence, dizziness, fatigue, irritability, and profuse sweating.
2. Osteoporosis resulting in bone fracture.
3. Pain symptoms such as arthralgia (join pain), headache, breast pain, back pain and muscle pain.
4. Nausea, vomiting, diarrhoea, indigestion, heartburn, and loss of appetite.
5. Cough, night sweats, breathlessness, and flu-like symptoms.
6. Skin irritation and swelling of hands or feet.
Caution should be taken before use to know if one has allergies to letrozole. If the patient is not completely menopausal, one should not take it. If the patient has current liver disease then that should be mentioned to doctor. FDA termed this drug as pregnancy category D, which means this can cause significant harm to unborn baby, therefore, it should be avoided administrating during pregnancy. If Femara is being given to a pre-menopausal patient, then proper care should be taken that the patient does not become pregnant. If a patient is breastfeeding, Femara administration should be avoided as it is still unknown if Femara passes into breast milk.
As known till now, Femara can interact with a total of 62 drugs and can show adverse effect within which two drugs are known to show severe side effects, which can outweigh the benefits.
1. Plavix cannot be taken with Femara as it can result in severe side effects such as visual disturbance, eye pain, floaters, memory loss, breathing difficulty, and wheezing as reported in few patients.
2. If Femara is being used for treating termination of pregnancy then it should never be combined with the use of Thalomid (thalidomide). Thalomid and Femara intake together can result in birth defects in newborns.
There are 57 other drugs which are shown to have moderate side effects when taken with Femara most of which are types of oestrogen derivatives.
Femara has shown greater efficiency than other anti-oestrogen drugs like tamoxifen. In 1998 International Breast Cancer Study Group (IBCSG) conducted a clinical trial known as BIG 1-98. In this study 8000 female with hormone receptor positive breast cancer were tested. Half of them were treated with tamoxifen and the other half were treated with Femara (letrozole) 2.5 mg tablets. After 60 months of treatment and 73 months of follow-up Femara was found to be more effective in reducing the risk of recurrence of breast cancer in patients. In adjuvant settings Femara have shown greater efficacy than tamoxifen.
Femara is a third generation aromatase inhibitor, which effectively blocks the production of oestrogen without blocking synthesis of other steroidogenic pathways, and has been termed as triumph of translational oncology. The vast range of indications for Femara in proper clinical settings is transforming the ways of managing hormone-sensitive breast cancer in postmenopausal women.
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Femara Review Article