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Generic name: testolactone [ TES-toe-LAK-tone ]
Brand name: Teslac

Testolactone is used for:

Treating certain types of breast cancer in women who have been through menopause or whose ovaries no longer function. It may also be used for other conditions as determined by your doctor.

Testolactone is an antineoplastic that is related to testosterone (male sex hormone) but has not been shown to have the masculine effects of testosterone. It works by blocking the production of estrogen, which helps prevent the growth of breast cancers that are activated by estrogen. It may also prevent tumor cells from being activated by other hormones.

Do NOT use testolactone if:

  • you are allergic to any ingredient in testolactone
  • you are a man with breast cancer
  • you are pregnant

Contact your doctor or health care provider right away if any of these apply to you.

Before using testolactone:

Some medical conditions may interact with testolactone. Tell your doctor or pharmacist if you have any medical conditions, especially if any of the following apply to you:

  • if you are pregnant, planning to become pregnant, or are breast-feeding
  • if you are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
  • if you have allergies to medicines, foods, or other substances
  • if you have heart disease (eg, ischemic heart disease), kidney disease, or liver problems
  • if you have high levels of calcium in your blood

Some MEDICINES MAY INTERACT with testolactone. Tell your health care provider if you are taking any other medicines, especially any of the following:

  • Anticoagulants (eg, warfarin) because the risk of side effects such as bleeding may be increased

This may not be a complete list of all interactions that may occur. Ask your health care provider if testolactone may interact with other medicines that you take. Check with your health care provider before you start, stop, or change the dose of any medicine.

How to use testolactone:

Use testolactone as directed by your doctor. Check the label on the medicine for exact dosing instructions.

  • Take testolactone by mouth with or without food.
  • If nausea, vomiting, or loss of appetite occur, check with your doctor or pharmacist for ways to lessen these effects.
  • Continue to use testolactone even if you feel well. Do not miss any doses.
  • If you miss a dose of testolactone, contact your doctor immediately.

Ask your health care provider any questions you may have about how to use testolactone.

Important safety information:

  • Lab tests, including calcium blood levels, may be performed while you use testolactone. These tests may be used to monitor your condition or check for side effects. Be sure to keep all doctor and lab appointments.
  • Use testolactone with caution in the ELDERLY; they may be more sensitive to its effects.
  • PREGNANCY and BREAST-FEEDING: Do not use testolactone if you are pregnant. If you think you may be pregnant, contact your doctor immediately. It is not known if this medicine is found in breast milk. If you are or will be breast-feeding while you use testolactone, check with your doctor. Discuss any possible risks to your baby.

Possible side effects of testolactone:

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome:

Abnormal skin sensations; aches of the legs and arms; general body discomfort; hair loss; loss of appetite; nausea; redness of the tongue; vomiting.

Seek medical attention right away if any of these SEVERE side effects occur:

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); confusion; dizziness; increased thirst or urination; severe drowsiness; severe muscle weakness; swelling of the hands or feet.

This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider. Call your doctor for medical advice about side effects. To report side effects to the appropriate agency, please read the Guide to Reporting Problems to FDA.

If OVERDOSE is suspected:

Contact 1-800-222-1222 (the American Association of Poison Control Centers), your local poison control center ( ), or emergency room immediately.

Proper storage of testolactone:

Store testolactone at room temperature, between 68 and 77 degrees F (20 and 25 degrees C). Store away from heat, moisture, and light. Do not store in the bathroom. Keep testolactone out of the reach of children and away from pets.

General information:

  • If you have any questions about testolactone, please talk with your doctor, pharmacist, or other health care provider.
  • Testolactone is to be used only by the patient for whom it is prescribed. Do not share it with other people.
  • If your symptoms do not improve or if they become worse, check with your doctor.
  • Check with your pharmacist about how to dispose of unused medicine.

This information is a summary only. It does not contain all information about testolactone. If you have questions about the medicine you are taking or would like more information, check with your doctor, pharmacist, or other health care provider.

Issue Date: June 3, 2015

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.