What Is Estramustine (Emcyt®)?

Reviewed by: HU Medical Review Board | Last reviewed: July 2022 | Last updated: July 2022

Emcyt® (estramustine) is a chemotherapy treatment option that has antineoplastic properties (meaning that it acts to prevent or halt the development and growth of tumors). It also has an estrogenic effect on cancer cells. It may be used in the palliative treatment of patients with metastatic (prostate cancer that has spread to the rest of the body) and/or progressive prostate cancer. Estramustine is an oral medication that comes in capsule form, and is taken at multiple times throughout the day. In some cases, estramustine may be used with other chemotherapies or hormone therapies. Individuals taking estramustine should also be monitored for changes in blood cell counts, mood changes, heart attacks, strokes, blood clots, liver function changes, changes in blood sugar levels, and serious infections.1,2

How does estramustine work?

Estramustine’s active ingredient has antineoplastic properties, meaning that it acts to prevent tumor growth and development. Estramustine does this by binding to the microtubules in a cell which play a key role in allowing cells to physically divide during the replication process. When a parent cell is unable to split into two daughter cells, it will eventually become too faulty and will die. When a cell manually kills itself because of a faulty cellular process it is called apoptosis. Chemotherapies cause cancer cells to stop dividing and undergo apoptosis, thus, slowing or halting the growth of a cancerous mass.

Cancerous cells are rapidly dividing while most other cells in our body aren’t, or are doing so at a slower rate. This property is what increases the chances of chemotherapies targeting cancer cells. However, there are still a few kinds of cells in our body that divide rapidly, such as hair cells or cells that line our intestines, which explains the common side effects of hair loss or gastrointestinal disruption while on certain chemotherapy medications. Blood cells, including important white blood cells, red blood cells, and platelets also divide on a somewhat regular basis, making it important to closely monitor someone on chemotherapy to make sure their blood cell counts aren’t dangerously low. If a person’s blood cell count dips below a certain threshold, they may be unable to receive treatment until the issue has resolved.

Estramustine also has an estrogenic effect on tumor cells. Prostate cancer tumors are often fueled to grow by androgens, including testosterone. Decreasing the body’s production of testosterone can potentially halt tumor growth. When a male is treated with estrogen-containing medications, it can prompt his body to stop making testosterone. This decrease in the important androgen could starve off tumor cells, limiting their ability to grow and spread. Other medications, such as steroids like prednisone, may also be prescribed with estramustine.3

What are the possible side effects of estramustine?

Multiple clinical trials evaluated the safety and efficacy of estramustine. The most common side effects of estramustine include nausea, swelling, changes in liver function, decreased white blood cells, decreased red blood cells, vomiting, male breast enlargement, and diarrhea. Many of these side effects are generally reversible and will be remedied when the medication is stopped. Your provider will be able to determine what side effects may be longer-lasting in nature. If you notice that your diarrhea and/or nausea are excessive, alert your provider. Excessive diarrhea could lead to dangerous dehydration. These are not all the possible side effects of estramustine. Talk to your doctor about what to expect or if you experience any changes that concern you during treatment with estramustine.

Things to note about estramustine

Several less common but more serious side effects can accompany estramustine including potentially developing a high blood pressure and blood clots which can increase your risk of having heart failure, a heart attack, or a stroke. Alert your provider immediately if you notice any of the following symptoms:

  • Slurred speech
  • Sudden vision changes
  • Swelling of the hands, feet, or legs
  • Signs of worsening diabetes like increased thirst or urination, or a change in blood sugar readings
  • Chest, jaw, or left arm pain
  • Weakness on one side of the body
  • Shortness of breath
  • Coughing up blood
  • Confusion
  • Dizziness or fainting

Additionally, there is a risk of developing very low white and red blood cell and platelet counts while taking estramustine. Your doctor will monitor you for any signs of this, however, it is important to self monitor for any signs of infection, shortness of breath, fatigue, unusual bruising, or bleeding. Specifically, a decrease in white blood cell count can increase your chance of developing a serious infection. Alert your provider immediately if you notice any signs of infection including:

  • Fever
  • Chills
  • Sore throat
  • Cough
  • Unusual bleeding or bruising

Before starting estramustine talk to your provider if you:

  • Have any problems with your liver or kidneys
  • Have high blood pressure or diabetes
  • Have any heart conditions or blood flow or clotting problems
  • Have depression
  • Have a history of seizures
  • Have a history of migraine headaches
  • Have anemia
  • Have bone disease
  • Have any allergies, including medication allergies
  • If you are sexually active and have a partner who may become pregnant
  • Have any other medical conditions
  • Are currently taking any other medications (prescription and over-the-counter), vitamins, or herbal supplements

You should also contact your provider if you notice any signs of an allergic reaction to the medication, including chest pain or difficulty breathing. Estramustine may also cause changes in liver function. Alert your provider immediately if you are experiencing stomach or abdominal pain, dark urine, or yellowing of the eyes or skin. It is also important to consult the prescribing information for any other medications taken with estramustine, including prednisone.

Receiving estramustine

Estramustine is administered orally and comes in capsule form. Your provider will determine the appropriate dosage and administration schedule for you, including your length of treatment and number of capsules taken daily. They will also determine the appropriate dosage and administration schedule of any other medications taken with estramustine, such as prednisone. It is important to follow your provided schedule exactly as instructed, and not to stop taking any prescribed medications on your own. The dose of your estramustine can be adjusted as needed by your provider. Patients should take their medication as prescribed by their doctor. Patients should talk to their doctor if they have any questions, or if they have questions regarding their estramustine regimen.

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