Estracyt (Estramustine)

How does it work?

Estracyt capsules contain the active ingredient estramustine sodium phosphate, which is a type of medicine called an alkylating agent. Estramustine is a combination of an oestrogen and chlormethine and works in two ways to treat prostate cancer.

Cancers form when some cells within the body multiply uncontrollably and abnormally. These cells spread, destroying nearby tissues. The chlormethine component of estramustine works by stopping the cancer cells from multiplying. It does this by binding to and damaging the DNA in the cancer cells. This stops the cells from growing and multiplying.

Estramustine also has a hormonal effect and works by reducing the production of testosterone. Prostate cancers are sensitive to testosterone and their growth is increased in the presence of this hormone. The oestrogen component of estramustine starves the prostate cancer cells of testosterone, which slows down their growth.

Both actions cause the prostate tumour to shrink.

What is it used for?

  • Prostate cancer.

Estracyt capsules are used to treat prostate cancer that has not responded to hormonal treatments to reduce the amount of testosterone in the body, for example diethylstilbestrol, or surgery to remove the testicles (orchidectomy). They may also be used if the cancer has relapsed after one of these treatments.

How do I take it?

  • Estracyt capsules should be swallowed whole with a glass of water. The capsules should not be chewed or broken.
  • Estracyt capsules should be taken at least one hour before or more than two hours after a meal.
  • This medicine should not be taken with milk or dairy products as this can reduce the amount of medicine absorbed into the blood.
  • The number of capsules you have to take will vary. The usual starting dose is four to six capsules in divided doses, ie two or three times a day. This will be changed by your doctor depending on how well you can tolerate the medicine and also on your response to the medicine.
  • It is important to follow the instructions given by your doctor. These will be printed on the dispensing label your pharmacist has put on the packet of medicine.


  • Chemotherapy medicines can decrease the number of blood cells in your blood. A low white blood cell count can increase your susceptibility to infections; a low red blood cell count causes anaemia and a low platelet count can cause problems with blood clotting. For this reason, you will need regular blood tests to monitor your blood cells during treatment with this medicine. Tell your doctor immediately if you experience any of the following symptoms during your treatment, as they may indicate problems with your blood cells: unexplained bruising or bleeding, purple spots, sore mouth or throat, mouth ulcers, high temperature (fever) or other signs of infection, or suddenly feeling tired, breathless, or generally unwell.
  • This medicine may increase the chance of getting a blood clot in a vein, eg in the leg (deep vein thrombosis) or in the lungs (pulmonary embolism), or a blood clot in an artery, eg causing a heart attack. Your doctor may prescribe you another medicine to reduce the risk of this. You should stop taking this medicine and inform your doctor immediately if you get any of the following symptoms during treatment: stabbing pains and/or unusual swelling, warmth or tenderness in an arm or leg, pain on breathing or coughing, coughing up blood, sudden breathlessness or sudden severe chest pain.

Use with caution in

  • Congestive heart failure.
  • Coronary artery disease.
  • People with moderate to severely low blood cell counts due to decreased blood cell production by the bone marrow.
  • Decreased kidney function.
  • Decreased liver function.
  • Diabetes.
  • People with a blood clot in a blood vessel (thrombosis), or inflammation of a blood vessel caused by a blood clot (thrombophlebitis).
  • People with disorders that increase the risk of blood clots in the blood vessels (thromboembolic disorders).
  • Hereditary blood disorders called porphyrias.
  • Epilepsy.
  • High blood pressure (hypertension).
  • People with high levels of calcium in the blood (hypercalcaemia).

Not to be used in

  • Children.
  • Severe disease involving the heart and blood vessels (cardiovascular disease).
  • Peptic ulcer.
  • Severe liver disease.

This medicine should not be used if you are allergic to any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.

If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Label warnings

  • Take this medication an hour before food or on an empty stomach.

Side effects

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here, it does not mean that all people using this medicine will experience that or any side effect.

  • Abnormal enlargement of breasts in men (gynaecomastia).
  • Impotence (erectile dysfunction).
  • Nausea and vomiting.
  • Fluid retention, sometimes causing swelling (oedema).
  • Diarrhoea.
  • Increased blood pressure.
  • Inability of the heart to pump blood efficiently (heart failure).
  • Formation of blood clots in the blood vessels (thromboembolism).
  • Heart attack.
  • Rash.
  • Problems with the liver.
  • Headache.
  • Fatigue.
  • Decrease in the number of white blood cells, red blood cells or platelets in the blood (leukopenia and neutropenia, anaemia, thrombocytopenia).
  • Confusion.
  • Depression.
  • Muscle weakness.
  • Severe swelling of lips, face, tongue or throat (angioedema – consult your doctor immediately if you experience this).

The side effects listed above may not include all of the side effects reported by the medicine's manufacturer.

For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect other medicines?

It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines during treatment this one, to ensure that the combination is safe.

Chemotherapy decreases the body's immune response. This means that vaccines may be less effective if given during treatment, and live vaccines may cause serious infections. Live vaccines include: measles, mumps, rubella, MMR, oral polio, oral typhoid and yellow fever. If live vaccines are needed they should be postponed until at least six months after finishing chemotherapy.

You should not take medicines containing calcium, for example calcium supplements, calcium-containing antacids or multivitamins that contain calcium at the same time of day as Estracyt capsules. This is because calcium can stop the medicine being properly absorbed from the gut and thus make it less effective.

Sodium clodronate can increase the amount of estramustine in the blood.

Other medicines containing the same active ingredient

There are currently no other medicines available in the UK that contain estramustine sodium phosphate as the active ingredient.