Testolactone (Teslac): Withdrawn Aromatase Inhibitor
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Testolactone: withdrawn status and what studies found

Former US strengths · Approval status · Half-life notes

What is testolactone?

Testolactone is an early aromatase inhibitor, a steroid-based drug that lowers estrogen by blocking its production from testosterone. It was sold in the US as Teslac tablets and injection, but both approvals were withdrawn, so no testolactone product is approved today.

Also known as: Teslac.

Former US strengths

Drugs@FDA lists Teslac 50 mg and 250 mg tablets and a 100 mg/mL injection, all discontinued.

Approval status and how it is used

FDA withdrew approval of Teslac injection (NDA 16-119) in 2010 and Teslac tablets (NDA 016118) in 2011, in both cases after Bristol-Myers Squibb said the products were no longer marketed.

Testolactone is named in the federal Schedule III list of anabolic steroids (21 CFR 1308.13(f)), so having it without a valid prescription is illegal. WADA lists it as an aromatase inhibitor (S4.1), banned in and out of competition.

It was studied with spironolactone in boys with familial male precocious puberty (Laue 1993), where control was lost over 2 to 4 years until a third drug was added. In six obese men, 6 weeks of testolactone raised average testosterone and LH and lowered estradiol (Zumoff 2003). Newer aromatase inhibitors such as anastrozole, letrozole and exemestane are the ones prescribed today.

Testolactone half-life and time to peak

  • Half-lifeNot listed
  • Time to peak (Tmax)Not listed

We could not find a Teslac label on DailyMed or Drugs@FDA, and the studies we cite give no half-life or time to peak, so we do not list one.

How to track testolactone in Dose Track

  1. Add testolactone as a custom compound. Start typing its name and Dose Track fills in the details from its research library for you to check, and it sits next to everything else you take.
  2. Log each tablet when you take it, including split or fractional tablets, so your history shows exactly what you took and when.
  3. Set reminders on your own schedule, whether that is daily, weekly or every few days.
  4. Your log is stored on your phone and no account is needed. Data only leaves it for features you choose, like AI answers and lab reading.

How Dose Track handles peptides · Reconstitution calculator · Half-life calculator

AnastrozoleArimidex · half-life about 2 days LetrozoleFemara · half-life about 2 days ExemestaneAromasin · half-life about 24 hours Tamoxifen CitrateNolvadex, Soltamox · half-life about 6 days

Frequently asked questions

What is the half-life of testolactone?+
We could not find a Teslac label on DailyMed or Drugs@FDA, and the studies we cite give no half-life or time to peak, so we do not list one.
Is testolactone (Teslac) still available?+
Not in the US. FDA withdrew the Teslac injection approval in 2010 and the tablet approval in 2011 after the maker stopped selling them. Anastrozole, letrozole and exemestane are current aromatase inhibitors.
Can I track testolactone in Dose Track?+
Yes. Testolactone is in Dose Track's research library, so when you add it as a custom compound its details are filled in for you to check. You can then log each tablet next to your other compounds, set reminders on your own schedule, and see your history next to your lab results. Your log is stored on your phone and no account is needed. Data only leaves it for features you choose, like AI answers and lab reading.

Sources

  1. Drugs@FDA: Teslac (testolactone) tablets, NDA 016118, marketing status.
  2. FDA. Bristol-Myers Squibb Co. et al.; withdrawal of approval of 70 new drug applications and 97 abbreviated new drug applications (includes Teslac tablets, NDA 016118). Federal Register, June 8, 2011.
  3. FDA. Novartis Pharmaceuticals Corp. et al.; withdrawal of approval of 27 new drug applications and 58 abbreviated new drug applications (includes Teslac injection, NDA 16-119). Federal Register, July 21, 2010.
  4. Laue L, et al. Treatment of familial male precocious puberty with spironolactone, testolactone, and deslorelin. J Clin Endocrinol Metab. 1993;76(1):151-155.
  5. Zumoff B, Miller LK, Strain GW. Reversal of the hypogonadotropic hypogonadism of obese men by administration of the aromatase inhibitor testolactone. Metabolism. 2003;52(9):1126-1128.
  6. 21 CFR 1308.13(f): Schedule III anabolic steroids. eCFR, October 2026.
  7. World Anti-Doping Agency. 2026 Prohibited List (S0 non-approved substances; S1 anabolic agents; S4.1 aromatase inhibitors; S4.4.1 metabolic modulators).

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