What are the Tamoxifen side effects?

Tamoxifen is a mixed estrogen agonist/antagonist drug primary used for the treatment of breast cancer in both premenopausal and postmenopausal women. Most of the types of breast cancer possess estrogen receptors, which are activated or stimulated by the presence of estrogen. Once stimulated they signal the increase in overall cell replication in the breast tissue. Here, Tamoxifen plays a vital role. Tamoxifen is converted into its active metabolite hydroxytamoxifen. It binds to the estrogen receptors but do not stimulate them rather prevent more estrogen from binding to the estrogen receptors. Thus it plays a role of competitive antagonist in the breast tissue, whereas in other tissues like uterus Tamoxifen plays a role of agonist and stimulates the estrogen receptors. Tamoxifen is marketed all over the globe with different brand names like Valodex, Istubal and Nolvadex.


What is Tamoxifen used for?

Although the most common and primary use for which Tamoxifen was discovered is the breast cancer, especially the estrogen receptor positive type, however, there are numerous other uses for which Tamoxifen gain popularity with the passage of time. Here are the few common uses of Tamoxifen:

  • Breast cancer – Tamoxifen is used for the treatment of breast cancer both in the men and the women. In women it can and is being used for the treatment of estrogen receptor positive breast cancer in both the pre and postmenopausal women. Numerous studies have shown that Anastrazole is a better option for the management of breast cancer in postmenopausal women. Moreover, it is also effective in estrogen receptor negative breast cancers.
  • Infertility – Tamoxifen induces ovulation and it is used for the treatment of infertility in women
  • Breast enlargement (Gynecomastia) – Tamoxifen is used for the management of unusual breast enlargement especially in women. It is taken both as the prophylaxis as well as after the onset of symptoms of breast enlargement. Other drug used for the same purpose is Clomiphene citrate.
  • Premature puberty – one of the most common conditions in which premature puberty occurs is McCune Albright Syndrome. Tamoxifen is used for the treatment of premature puberty and alters the final adult height of an individual, which may be retarded due to excessive estrogen.
  • Psychiatric use – Tamoxifen is used for the management of manic episodes in patients having Bipolar disorder
  • Retrperitoneal fibrosis – it is not a well documented use of Tamoxifen.
  • Thyroid conditions – Tamoxifen is used for the management of Reidel’s thyroiditis as an adjunct therapy.

What are the common side effects of Tamoxifen?

Common side effects of Tamoxifen are:

  • Prevention of osteoporosis – usually side effects are considered only as adverse or detrimental effects of a drug in the human body. Tamoxifen plays a special role in the prevention of treatment of osteoporosis because it is an estrogen receptor agonist in the bones.
  • Endometrial carcinoma – according to few studies, Tamoxifen has been labeled as a carcinogen. It increases the risk of malignant changes in the endometrium of the uterus and thus predisposes to endometrial carcinoma
  • Lipid profile – Tamoxifen deranges the lipid profile of the blood. Few studies support that it plays an important role in controlling the lipid level of the blood, however in few cases the level of triglycerides have been increased during the use of this drug.
  • Cardiovascular complications – as it deranges the lipid profile it may predispose to an individual to cardiovascular and neurovascular complications. Moreover, it Tamoxifen increases the risk of thromboembolism in healthy individuals.
  • Liver – chronic use of Tamoxifen may cause steatohepatitis or fatty liver. In these cases liver functions tests are usually abnormal. It may increase the risk of developing hepatocellular carcinoma
  • Nervous disorders – Tamoxifen use impairs the cognition of an individual. Moreover, both long term and short term memory is affected.
  • Sexual dysfunction – Tamoxifen use causes decreased libido in both men and women
  • General side effects like nausea, confusion, jaundice, fatigue, drowsiness, blurring of vision, easy bruising, thinning of hair, hot flashes, fever, chills, and symptoms of flu are also occasionally observed while using Tamoxifen.

What are the side effects of Tamoxifen on children?

The major side effect in children is that it may act as an estrogen receptor agonist in the skeletal system and cause premature or early fusion of the bones resulting in decreased bone development and short stature. So, it is always avoided in the growing age group.

What are the side effects of Tamoxifen on men?

The most common side effect of Tamoxifen in men is sexual dysfunction. Erectile dysfunction may also occur with decreased libido. All these factors contribute to impotence.

What are the side effects of Tamoxifen on women?

The most common side effect of Tamoxifen is endometrial carcinoma of the uterus. Tamoxifen is an estrogen receptor agonist/antagonist. While it exerts antagonist effect in the breast tissue, in uterine tissue it has an agonist effect, which stimulates the uterine tissue replication leading to endometrial carcinoma.

Another common side effect for postmenopausal women is prevention or delaying of onset of osteoporosis. Usually, postmenopausal women are likely to develop osteoporosis due to estrogen deficiency.

Tamoxifen causes vaginal dryness and itchiness in the women. Moreover, it decreases the sexual desire in women. It also causes menstrual irregularities and unusual vaginal bleeding in women.

What are the side effects of Tamoxifen on pregnant women?

Tamoxifen is classified as category D drug in pregnant women. It is contraindicated in the pregnant women or the women planning to conceive. Studies have shown that it increases the risk of implantation failure, low birth weight, congenital malformations, miscarriages and vaginal bleeding. Tamoxifen decreases the milk secretion from the breasts. It is also contraindicated in nursing mothers due to the side effects in breast fed baby.

What are the side effects of Tamoxifen on elderly?

In elderly women more than fifty years of age, there are four to five times increased risk of developing endometrial carcinoma as compared to the other age group due to Tamoxifen.

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