Why does Tamoxifen cause clots, edema, hypercalcemia & elevated triglycerides/cholesterol?

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I am studying for my NCLEX and these side effects are listed and I can't remember these side effects if I have no idea what causes them!

I do know that Tamoxifen is an antiestrogen that decreases the effects of estrogen by blocking estrogen in estrogen-sensitive tumors...I'm specifically studying Uterine cancer.

And I know that contraception increases clots, but why would an antiestrogen increase clots? Wouldnt it be the opposite then?...... Or maybe because Tamoxifen decreases Estrogen there must be an increase in Progesterone to balance out the decreased Estrogen? And if there is an increase in Progesterone, there's an increase in clots??

So confused...

Also I have no idea where those electrolyte imbalances are coming from either...

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Specializes in ICU, LTACH, Internal Medicine.

Tamoxifen is not estrogen antagonist. It works as competitive antagonist in only two groups of tissue: breast and endomethrium. In all other places it works as estrogen receptor modulator. This latter effect is not directly dose dependent, not predictable in degree and can vary anywhere from pure agonist to partial competitive antagonist. We cannot predict it in every single case but most side effects of tamoxifen are caused by overstimulation of estrogen receptors in places other than breast and endomethrium.

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Specializes in Trauma, Orthopedics.

I honestly think you're studying too hard if you think this will be on the NCLEX.

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AH! Thank you SO much KatieMI ! It makes so much more sense now.

So basically, Tamoxifen side effects are r/t stimulation of estrogen outside the breast/uterus.

And with the breast and uterus, it binds to a receptor but does not activate the receptor, causing decrease estrogen effects only related to uterus/breast involvement !!!

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flyersfan88, BSN, RN, if I don't understand how Tamoxifen works then I can't understand the side effects of it. I need to know the side effects for Tamoxifen because it is the primary hormone therapy given to patients with early stages of breast cancer and those with metastatic breast cancer. I also might need to explain to future patients, obviously in simple terms, why they experience these side effects.

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Specializes in ICU, LTACH, Internal Medicine.

Yeah, you got it. Welcome to the wonderful world of REAL pharmacology!

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Specializes in MICU.

One of the side effect of Tamoxifen (mostly chemotherapy drugs) is bone marrow suppression. The bone becomes weak and excess calcium leaks into the blood which will cause hypercalcemia.

One of the major roles of kidney is to filter excess minerals. This means the kidney has to work harder to filter out the excess calcium, if the kidney becomes impaired, the kidney holds on to Na which will cause water retention (edema) because water follows sodium.

Excess calcium in the blood leads to abnormal blood clot

I hope this helps

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Thanks loveofrn!! Your explanation helped tons. I had trouble connecting all the dots. I didn't even think bone marrow suppression = hypercalcemia. And everything after that just follows

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Specializes in Trauma, Orthopedics.
flyersfan88, BSN, RN, if I don't understand how Tamoxifen works then I can't understand the side effects of it. I need to know the side effects for Tamoxifen because it is the primary hormone therapy given to patients with early stages of breast cancer and those with metastatic breast cancer. I also might need to explain to future patients, obviously in simple terms, why they experience these side effects.

Is that how I do my job?! Wow, thanks!

But really, good luck to you....and ease up. NCLEX is more concerned with delegating than anything of actual substance.

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Is that how I do my job?! Wow, thanks!

But really, good luck to you....and ease up. NCLEX is more concerned with delegating than anything of actual substance.

I'm sorry flyersfan88, BSN, RN I didn't mean to be offensive. I just have trouble remembering main concepts (in this instance, the common side effects for a hormonal cancer therapy) if I don't understand the "why" behind it. Also - I can't teach my patients about their treatment side effects if I don't remember them lol.

I've heard NCLEX has increased the number of delegating questions!.. but I also think it's important to know the basic content, which helps with delegation

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Loveofrn you taught that well!

Thank you!

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