Arimidex (anastrozole) is a non-steroidal drug which is used to treat breast cancer. It has been thoroughly studied in women with breast cancer between the 5th-8th decades of life. There are some breast cancers which are dependent on estrogen for their growth. Arimidex acts by suppressing the levels of estrogen in the body and thus reduces the growth of breast cancer. The drug is first line treatment in post menopausal women with early breast cancer or in those with advanced breast cancer despite taking tamoxifen. Arimidex is often combined with other drugs to treat breast cancer in post menopausal women. The drug has been used to treat early or advanced breast cancer in women all cultures and races.
Arimidex is not a large molecule but still it is not very soluble in water. Because of its organic structure, it is more soluble in alcohols like methanol, acetone, ethanol and acetonitrile. When taken orally, Arimidex enters the liver where more than 90% is broken down into inactive metabolites. In individuals who have mild liver disease, cirrhosis or have alcoholic liver problems, the drug is safe. However, in individuals with severe liver disease, the drug does have the potential to cause side effects.
Because Arimidex is not excreted in the urine, people with kidney impairment can take the drug without any dosage changes. Further, the drug dosage does not have to be altered in the elderly individuals either.
Arimidex in the US is administered by physicians who specialize in the treatment of cancer. Arimidex is sold as a pill containing 1 mg of anastrozole. The formulation of the pill also contains other inactive chemicals like lactose, magnesium sterate, polyethylene glycol, sodium starch glycolate and titanium dioxide. These ingredients make the active anastrozole more soluble in water, and make it easier to prepare as a pill.
Arimidex is taken orally everyday as a 1-mg tablet. All the patients with advanced breast cancer who have been prescribed the drug take it until a response in the tumor is seen. For those patients who take Arimidex as part of adjuvant (a substance that helps and enhances the pharmacological effect of a drug) therapy, the exact duration of the treatment remains unknown but most experts recommend that women take it for 5 years.
Mode of Action
Some breast cancers have estrogen receptors and these breast caners are stimulated to grow by the estrogen in the body. In post menopausal women, the primary source of estrogen is from the conversion of androstenendione (made in the adrenal gland) in the fatty tissues to estrone. In the fatty tissues there is an enzyme known as Aromatase which can covert this hormone into estradiol, the female sex hormone. Studies have also shown that some breast cancers also contain this enzyme, aromatase. In the days gone by, one of the ways to decrease the levels of estrogen in the body was by removing the ovaries. Today, however, anti-estrogen drugs are preferred to surgery. One of the first anti-estrogen drug used to treat breast cancer was tamoxifen. Numerous trials have shown that anti-estrogen drugs can significantly decrease breast cancer size.
Indications for Arimidex
Arimidex has three general indications:
- Arimidex is recommended for the treatment of post menopausal women who have early breast cancer which is hormone sensitive (estrogen positive).
- It is also indicated as the first line treatment of post menopausal females who have spread of breast cancer either locally or systemically, irrespective of the hormonal status of the breast cancer.
- It is also indicated in the treatment of advanced breast cancer in post menopausal women who have further growth of breast cancer following treatment with tamoxifen. Women who do not have estrogen receptor positive breast cancer and those who do not show any response to tamoxifen generally do not respond to Arimidex.
Arimidex has been studied quite well in the laboratory for its side effects. Further, its side effects in humans have been well recorded in a number of clinical trials. From these clinical studies, it is estimated that at least 5% of individuals who do take Arimidex develop a variety of side effects in varying range of severity. The most common side effects of the drug include:
fatigue and general malaise
vague body pains
abdominal cramps and bloating
constipation, diarrhea, gastric upset
swelling of the legs
high cholesterol levels
vague muscle and joint pains
softening of bone (osteoporosis)
fractures and bone pain
mood changes- depression, lack of sleep, anxiety
Clots in the legs
Cancer of the uterus
Besides general tiredness, the next most common complain of patients who take Arimidex is joint and bony pain. Infact fractures of spine, hip and wrist are all increased in patients who take Arimidex for long periods. Despite the wide range of side effects, Arimidex is generally well tolerated by the majority of women.
In humans, the drug is generally safe and even at high doses the symptoms are mild and vague. Most individuals who overdose on Arimidex complain of stomach upset, bleeding or gastritis. There is no specific treatment of drug over dose and care is usually supportive. However, it is highly recommended that the patient be observed in a hospital if an over dosage has occurred. Individuals who have a history of allergies or develop a skin rash to Arimidex should refrain from taking it
To begin with, Arimidex is not medically recommended for use in body builders or for the treatment of any medical disorder in men. All the data about Arimidex on body builders has been empirically derived by trial and error.
One of the chief reasons why Arimidex is used by body builders is to decrease the side effects which usually occur after the use of other anabolic steroids. The majority of anabolic steroids will cause breast enlargement, loss of hair and water retention. Arimidex with its ability to block the synthesis of estrogen can alleviate some of these embarrassing and obvious side effects of anabolic steroids. Plus, it has been observed that the 1mg dose of Arimidex can also increase the levels of testosterone. In the past, most body builders used drugs like Nolvadex or Proviron against the excess estrogen, but many prefer Arimidex because its actions are rapid and effective. Individuals who use Arimidex for this purpose suggest a starting dose of 0.25 mg/day. Only if no response is seen after a few months, should the dose be increased to 0.5-1.0 mg. The great thing about Arimidex is that it can be used with a variety of anabolic steroids.
However, a word of caution. Anyone who takes Arimidex should get routine measurements of the estrogen levels in the blood. Complete suppression of estrogen can lead to decreases in HDL (good cholesterol). And this can lead to premature development of heart disease.
Concerns about Arimidex
Arimidex is not supposed to be taken by women who are pregnant because there is a concern that it may cause damage to the fetus. While all these studies have been done in animals, there is concern that the drug may have similar effects in human pregnant female. If a pregnant female does take Arimidex, the patient should be appropriately counseled on the risk versus the benefit because there is potential to lose the fetus.
Arimidex in general is never administered to premenopausal females. All women who do receive the drug always require a pregnancy test first.
All women who take Arimidex should be carefully followed up and their bone density regularly assessed. The drug is known to worsen osteoporosis and increase the incidence of fractures. Arimidex also causes an increase in the levels of blood cholesterol.
In animals at least, the drug has been shown to induce cancers at very high doses. This is the chief reason why Arimidex should not be taken for more than 5 years in humans.
Arimidex is not for use in children and its safety has not been established in this age group.