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Generic name: testolactone (test O lack tone)
Brand name: Teslac
Drug class: Aromatase inhibitors, Hormones / antineoplastics

What is testolactone?

Testolactone blocks the production of the hormone estrogen. Certain types of breast cancer require estrogen to grow.

Testolactone is used to treat some types of breast cancer.

Testolactone may also be used for purposes other than those listed in this medication guide.

What is the most important information I should know about testolactone?

Testolactone should not be used for the treatment of men with breast cancer or in patients with a history of allergic reactions to the drug.

What should I discuss with my healthcare provider before taking testolactone?

Testolactone should not be used for the treatment of men with breast cancer or in patients with a history of allergic reactions to the drug.

Testolactone is in the FDA pregnancy category C. This means that it is not known whether testolactone will be harmful to an unborn baby. Do not take this medication without first talking to your doctor if you are pregnant or could become pregnant during treatment.

Testolactone passes into breast milk in small amounts and may affect a nursing baby. Do not take testolactone without first talking to your doctor if you are breast-feeding a baby.

How should I take testolactone?

Take testolactone exactly as directed by your doctor. If you do not understand these directions, ask your pharmacist, nurse, or doctor to explain them to you.

Take each dose with a full glass (8 ounces) of water.

It is important to take testolactone regularly to get the most benefit.

Your doctor may want you to have breast exams (or to perform self breast exams), mammograms, blood tests, or other medical evaluations during treatment with testolactone to monitor progress and side effects.

Store testolactone at room temperature away from moisture and heat. Keep this product out of the reach of children.

What happens if I miss a dose?

Take the missed dose as soon as you remember. However, if it is almost time for the next dose, skip the missed dose and take only the next regularly scheduled dose. Do not take a double dose of this medication unless your doctor directs otherwise.

What happens if I overdose?

Call an emergency room or a poison control center for advice if you suspect an overdose.

Symptoms of a testolactone overdose are unknown, but nausea, vomiting, seizures, tremor, or dizziness may be expected.

What should I avoid while taking testolactone?

There are no restrictions on food, beverages, or activity during treatment with testolactone unless otherwise directed by your doctor.

Testolactone side effects

Stop taking testolactone and seek emergency medical attention or contact your doctor immediately if you experience any of the following serious side effects:

  • an allergic reaction (difficulty breathing; closing of the throat; swelling of the lips, tongue, or face; or hives);

  • new breast lumps;

  • bone pain;

  • menstrual changes, abnormal vaginal bleeding, vaginal discharge, or pelvic pain or pressure; or

  • excessive nausea, vomiting, or thirst.

Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome.

Testolactone dosing information

Usual Adult Dose for Breast Cancer--Palliative:

For use as adjunctive therapy in the palliative treatment of advanced or disseminated breast cancer in postmenopausal women when hormonal therapy is indicated or in women who were diagnosed as having had disseminated breast carcinoma when premenopausal, in whom ovarian function has been subsequently terminated: 250 mg 4 times a day.

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What other drugs will affect testolactone?

Before taking testolactone, tell your doctor if you are taking

  • an estrogen such as Premarin, Ogen, Estratest, Estraderm, Vivelle, Climara, and others;

  • a birth control pill that contains estrogen;

  • warfarin (Coumadin) or another blood thinner.

You may not be able to take testolactone or you may require special monitoring or a dosage adjustment if you are taking any of the medicines listed above.

Drugs other than those listed here may also interact with testolactone. Talk to your doctor and pharmacist before taking any prescription or over-the-counter medicines, including herbal products.

Further information

  • Your pharmacist has additional information about testolactone written for health professionals that you may read.

What does my medication look like?

Testolactone is available with a prescription under the brand name Teslac. Other brand or generic formulations may also be available. Ask your pharmacist any questions you have about this medication, especially if it is new to you.

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

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