Tamoxifen is

Appeared in: KPSC Staff Nurse - 2021

Explanation

Tamoxifen is a Selective Estrogen Receptor Modulator (SERM) that acts as a competitive antagonist at estrogen receptors in breast tissue.
This antagonistic action blocks estrogen from stimulating the growth of hormone-receptor-positive breast cancer cells.
While it is an antagonist in the breast, it has partial agonist (estrogen-like) effects in other tissues like the bone and uterus.

Option A: Although Tamoxifen has estrogen agonist effects in some tissues (like bone and endometrium), its primary therapeutic effect in breast cancer treatment is as an antagonist. Therefore, classifying it simply as an agonist is incorrect and misleading.
Option B: Tamoxifen's mechanism of action is related to estrogen receptors, not progesterone receptors. It does not have progesterone agonist activity.
Option D: Tamoxifen does not act on progesterone receptors. Its effects are specific to estrogen receptors.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Pharmacology and Mechanism of Action of Tamoxifen as background academic context rather than a clinical decision trigger.
Tamoxifen is a cornerstone in the treatment and prevention of ER-positive breast cancer, significantly improving survival rates. Nurses play a vital role in managing its side effects and educating patients.
A key patient safety concern is the increased risk of endometrial cancer and venous thromboembolism (VTE). Nurses must educate patients to immediately report any abnormal vaginal bleeding, leg swelling, or sudden shortness of breath.
What if? If a postmenopausal patient on Tamoxifen reports abnormal vaginal bleeding, it should not be dismissed as a normal side effect. It requires immediate investigation, including a potential endometrial biopsy, to rule out endometrial hyperplasia or cancer.

How to Approach the Question

First, identify the drug mentioned in the stem: Tamoxifen.
Recall the pharmacological class of Tamoxifen. It is a well-known drug in oncology and gynecology.
Recognize that Tamoxifen is a Selective Estrogen Receptor Modulator (SERM), meaning its action is tissue-specific.
Consider its primary clinical use: treating estrogen-receptor-positive breast cancer. For this purpose, it must block estrogen's effect on breast tissue.
Evaluate the options based on this primary action. 'Estrogen antagonist' best describes its effect in breast cancer.
Eliminate the progesterone-related options as Tamoxifen acts on estrogen receptors. Differentiate between its antagonist action in the breast and its partial agonist action elsewhere to select the most appropriate answer for its main therapeutic role.

Concept Tested & Keywords

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E6 Pharmacology Katzung 16e pp. 1145-1147, 1147-1149

E6 Gynecology Williams p. 183-219

Practise the full KPSC Staff Nurse - 2021

Attempt every question from this paper in a timed mock, then review the full solution for each one.