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Created Feb 2021


  • [TEOLIT]
  • [TESLAC]


DEA CODE 4000: Schedule 3

  • Testolactone is a synthetic drug related to the male hormone testosterone.
  • It is used to reduce the size of tumors in some women with advanced breast cancer.
  • Testolactone is available in the U.S. under the brand name Teslac.
  • It is never used in treating breast cancer in men.
  • Testolactone is approved by the United States Food and Drug Administration (FDA)
  • Its cost usually is covered by insurance.
  • It is classified as an antineoplastic agent, which means that it stops or slows the growth of malignant cells.

One advantage of testolactone is that, although it is related to testosterone, it does not cause women to develop male characteristics such as a deep voice or facial hair.

As noted above, testolactone is related to the male hormone testosterone. The way in which it inhibits the growth of breast cancer cells is not clear. However, it is known that the hormone estrogen stimulates the growth of some breast cancer cells, and testolactone seems to interfere with estrogen production. The resulting reduction in estrogen levels may slow the growth of breast cancers sensitive to this hormone.

In breast cancer, testolactone is a palliative treatment. This means that it helps relieve symptoms, but does not cure the cancer. It is effective only in about 15% of the women who take it. In these women, however, it helps reduce the size of half or more tumors. Normally testolactone is used along with other chemotherapy drugs for fighting advanced breast cancer.

Testolactone blocks the body from making estrogen. It is used to treat advanced breast cancer in women.

What may interact with it?

  • Female hormones, like estrogens or progestins and birth control pills
  • Some herbal products with estrogen or estrogen-like ingredients
  • Warfarin

What should I watch for while using it?

  • Visit your doctor for regular check ups.
  • Tell your doctor if you have any unusual effects while you are taking this medicine.
  • You will need important blood work done while you are taking this medicine.

  • Testolactone (Teslac brand name) is an anti-cancer agent, which was used as adjunctive therapy in the palliative treatment of advanced or disseminated breast cancer.
  • The mechanism of testolactone action is reported to be related to the inhibition of aromatase enzymatic activity.
  • Testolactone is no longer available in the USA.

  • Testolactone, also known as teslac, belongs to the class of organic compounds known as naphthopyrans.
  • Considered to be a steroid lipid molecule
  • Used for palliative treatment of advanced breast cancer in postmenopausal women
  • It works by blocking the production of estrogens, which helps prevent the growth of breast cancers that are stimulated by estrogens.
  • Testolactone is a very hydrophobic molecule, practically insoluble (in water), and relatively neutral.

Many medicines have not been studied specifically in older people. Therefore, it may not be known whether they work exactly the same way they do in younger adults or if they cause different side effects or problems in older people.

There is no specific information comparing use of testolactone in the elderly with use in other age groups.

Other Medical Problems:
The presence of other medical problems may affect the use of this medicine. Make sure you tell your doctor if you have any other medical problems, especially:

  • Heart or kidney disease


  • Absorption:
    Readily absorbed from GI tract
  • Metabolism:
    Metabolized in liver
  • Elimination:
    Excreted in urine


Drug Interactions (27)

What other drugs will affect Testolactone?

A total of 27 drugs are known to interact with Thiopental.

  • 1 major drug interaction
    • carfilzomib
  • 26 moderate drug interactions

Teslac tablets discontinued (2008):
Bristol-Myers Squibb has discontinued the manufacturing of Teslac (testolactone) 50mg tablets. Once current inventories are depleted, Teslac will no longer be available in the United States. Healthcare providers should begin to convert Teslac-treated patients to alternative therapies.

Pharmacycode PDF Teslac
Use in Bodybuilding:

Testolactone was first approved as a prescription drug by the FDA back in 1970. It was an early anti-estrogenic drug, exhibiting a moderately pronounced effect but failing to reach levels of high clinical success. As other more effective medications began to surface for the treatment of breast cancer, testolactone would not see the success its developers likely planned for it. It would see production in a small number of countries outside the U.S., most notably Brazil, Germany, and Chile. It has since been discontinued in all countries but the U.S., where the Teslac brand is still available.

Testolactone is no longer commonly used in clinical medicine, and consequently is not manufactured on a large sale globally. Presently a small number of testolactone preparations still exist, but are not commonly diverted for sale on the black market given the very low demand for the drug in this population.

Bodybuilders reference:
Teslac is used as an anti-estrogen. Instead of acting as an estrogen antagonist (competing for estrogen receptor-sites), Teslac prevents the aromatization of androgens into estrogens by inhibiting the aromatase enzyme. Obviously this prevents or minimizes the negative effects of estrogen such as gyno, water retention, and female pattern fat deposits. Teslac is unique in that it is reputed to cause permanent irreversible suppression of estrogen production in males.

Technically speaking, Teslac is an oral androgenic steroid related to testosterone. However, it has only very low androgenic and no anabolic effect. For male athletes, it is probably the best anti-estrogen available, and it causes an increase in natural (endogenous) testosterone production.

Manufacturer inserts suggest a dosage of 250-1000mg daily. However, this is not reported as necessary for estrogen suppression. Normally 200-300mg daily divided into 2-3 doses was reported as quite effective. Some reported 100-mg of the injection form version was even more effective. Due to the high price of Teslac, many have stacked it with PROVIRON: Teslac-100-mg daily and Proviron 50-mg daily. Women users reported excellent hardening effects with few, if any, side effects such as virilization.

Obsolete for Battling Breast Cancer:
Similar to mesterolone, testolactone is an anabolic steroid that is primarily used for its ability to combat estrogen-related side effects and not the muscle-building properties of the compound. Like most drugs which feature "anti-estrogen" effects, testolactone was first manufactured and prescribed for the treatment of estrogen dependent breast cancer, as it is a first generation non-selective steroidal aromatase inhibitor. Testolactone is able to inhibit the aromatase enzyme noncompetitively and irreversibly, thereby limiting estrogen production in the body. However with the discovery and subsequent availability of more potent and effective drugs for this purpose, testolactone has seemingly been deemed obsolete for the purpose of battling breast cancer.

Two Advantages:
Even though the drug no longer being utilized for its originally intended purpose, testolactone still offers several unique advantages for steroid users. First, research has shown that the compound can effectively treat and prevent gynocomastia. This is seemingly accomplished by way of aromatase inhibition as opposed to the estrogen agonist/antagonist mechanism that tamoxifen citrate accomplished this effect with. The second benefit that strength athletes, bodybuilders and other who make use of performance-enhancing drugs could experience by taking testolactone is the ability of the compound to help increase the natural testosterone production of users. This increase is prompted by several physiological mechanisms.

  • A non-selective, irreversible, steroidal aromatase inhibitor
  • Used for treating various types of breast cancer in women who have been through menopause or whose ovaries no longer function.
  • It works by blocking the production of estrogens, which helps prevent the growth of breast cancers that are stimulated by estrogens
  • First approved for medical use in the United States in 1970
  • Discontinued in 2008 and is no longer available for medical use
  • Still marketed in the United States under the brand name Teslac

Testolactone is used to treat breast cancer at a dosage of 250 mg four times per day by mouth or 100 mg three times per week by intramuscular injection.

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