Enobosarm, GTx-024, MK-2866, S-22


Overview Information

Ostarine is an investigational drug that has not yet been approved by the US Food and Drug Administration (FDA). It is part of a class of drugs called selective androgen receptor modulators (SARMs). Some supplement companies have included ostarine in products for bodybuilding. The FDA considers supplements containing ostarine to be illegal.

Ostarine is used by mouth to improve athletic performance and for involuntary weight loss in people who are very ill, also known as cachexia or wasting syndrome. But there is very little good scientific research to support these uses.

How does it work?

Ostarine attaches to proteins in the body known as androgen receptors. When ostarine binds to these receptors, it tells the muscles in the body to grow. Unlike some other chemicals that bind to androgen receptors, such as steroids, ostarine doesn't seem to cause as many side effects in other parts of the body.

Uses & Effectiveness?

Insufficient Evidence for

  • Involuntary weight loss in people who are very ill (cachexia or wasting syndrome). Early research shows that taking ostarine can increase lean body mass by a small amount in cancer patients who seem to be losing weight.
  • Age-related muscle loss (sarcopenia). Early research shows that taking ostarine can increase lean body mass by a small amount in elderly adults.
  • A group of inherited disorders that cause muscle weakness and muscle loss (muscular dystrophy).
  • Breast cancer.
  • Loss of bladder control (urinary incontinence).
  • Other conditions.
More evidence is needed to rate ostarine for these uses.
Side Effects

Side Effects & Safety

When taken by mouth: Ostarine is POSSIBLY UNSAFE when taken by mouth. Liver damage has been reported in some people taking ostarine. Other common side effects of ostarine include stomach pain, constipation, diarrhea, headache, nausea, fever, heart attack, and stroke.

Special Precautions & Warnings:

Pregnancy and breast-feeding: There isn't enough reliable information to know if ostarine is safe to use when pregnant or breast-feeding. Stay on the safe side and avoid use.

Liver problems: Ostarine might cause liver problems in some people. People with a history of liver problems should avoid ostarine.



We currently have no information for OSTARINE Interactions.



The appropriate dose of ostarine depends on several factors such as the user's age, health, and several other conditions. At this time there is not enough scientific information to determine an appropriate range of doses for ostarine. Keep in mind that natural products are not always necessarily safe and dosages can be important. Be sure to follow relevant directions on product labels and consult your pharmacist or physician or other healthcare professional before using.

View References


  • 2017-18 NCAA Banned Drugs List. National Collegiate Athletic Association (NCAA), June 5, 2017. https://www.ncaa.org/2017-18-ncaa-banned-drugs-list. Accessed: Sept 7, 2017
  • Coss CC, Jones A, Dalton JT. Pharmacokinetic drug interactions of the selective androgen receptor modulator GTx-024 (enobosarm) with itraconazole, rifampin, probenecid, celecoxib and rosuvastatin. Invest New Drugs 2016;34(4):458-67. View abstract.
  • Dalton JT, Barnette KG, Bohl CE, et al. The selective androgen receptor modulator GTx-024 (enobosarm) improves lean body mass and physical function in healthy elderly men and postmenopausal women: results of a double-blind, placebo-controlled phase II trial. J Cachexia Sarcopenia Muscle 2011;2(3):153-61. View abstract.
  • Dart DA, Kandil S, Tommasini-Ghelfi S, et al. Novel trifluoromethylated enobosarm analogues with potent antiandrogenic activity in vitro and tissue selectivity in vivo. Mol Cancer Ther 2018;17(9):1846-58. View abstract.
  • Dobs AS, Boccia RV, Croot CC, et al. Effects of enobosarm on muscle wasting and physical function in patients with cancer: a double-blind, randomised controlled phase 2 trial. Lancet Oncol 2013;14(4):335-45. View abstract.
  • Dubois V, Simitsidellis I, Laurent MR, et al. Enobosarm (GTx-024) modulates adult skeletal muscle mass independently of the androgen receptor in the satellite cell lineage. Endocrinology 2015;156(12):4522-33. View abstract.
  • Dynamic Technical Formulations, LLC. Issues a Voluntary Nationwide Recall of Tri-Ton Due to the Presence of Andarine and Ostarine. FDA Recalls, Market Withdrawals, & Safety Alerts, May 19, 2017. https://www.fda.gov/Safety/Recalls/ucm559700.htm?source=govdelivery&utm_medium=email&utm_source=govdelivery. Accessed: Sept 7, 2017.
  • FDA. FDA Warns against using SARMs in body building products. October 2017. Available at: https://www.fda.gov/newsevents/newsroom/fdainbrief/ucm583021.htm.
  • Selective Androgen Receptor Modulators (SARMs) - A Prohibited Class of Anabolic Agents. U.S. Anti-Doping Agency, November 18, 2015. https://www.usada.org/selective-androgen-receptor-modulators-sarms-prohibited-class-anabolic-agencts/. Accessed: August 30, 2017.
  • Thevis M, Geyer H, Thomas A, Schänzer W. Trafficking of drug candidates relevant for sports drug testing: detection of non-approved therapeutics categorized as anabolic and gene doping agents in products distributed via the Internet. Drug Test Anal 2011;3(5):331-6. View abstract.
  • USADA. Athlete Advisory: Ostarine in Supplements. July 2017. Available at: https://www.usada.org/growing-evidence-ostarine-athlete-risk/.
  • Van Wagoner RM, Eichner A, Bhasin S, Deuster PA, Eichner D. Chemical composition and labeling of substances marketed as selective androgen receptor modulators and sold via the internet. JAMA 2017;318(20):2004-10. View abstract.
  • WADA. What is prohibited. 2019 list of prohibited substances and methods. Available at: https://www.wada-ama.org/en/content/what-is-prohibited/.
  • Warning Letter: Infantry Labs LLC 10/23/17. FDA Inspections, Compliance, Enforcement, and Criminal Investigations, October 23, 2017. https://www.fda.gov/iceci/enforcementactions/warningletters/2017/ucm582685.htm. Accessed: November 1, 2017
  • Warning Letter: Ironmag Labs 10/23/17. FDA Inspections, Compliance, Enforcement, and Criminal Investigations, October 23, 2017. https://www.fda.gov/iceci/enforcementactions/warningletters/2017/ucm582464.htm Accessed: November 1, 2017
  • Warning Letter: Panther Sports Nutrition 10/23/17. FDA Inspections, Compliance, Enforcement, and Criminal Investigations, October 23, 2017. https://www.fda.gov/iceci/enforcementactions/warningletters/2017/ucm581630.htm. Accessed: November 1, 2017

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CONDITIONS OF USE AND IMPORTANT INFORMATION: This information is meant to supplement, not replace advice from your doctor or healthcare provider and is not meant to cover all possible uses, precautions, interactions or adverse effects. This information may not fit your specific health circumstances. Never delay or disregard seeking professional medical advice from your doctor or other qualified health care provider because of something you have read on WebMD. You should always speak with your doctor or health care professional before you start, stop, or change any prescribed part of your health care plan or treatment and to determine what course of therapy is right for you.

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