1 year ago


•     [9-alpha-fluoro-11-beta-hydroxy-17-alpha-methyl-4-androstene-3-one,17b-ol]
•     Molecular Weight: 336.4457
•     Formula: C20 H29 F O3
•     Melting Point: 240C
•     Manufacturer: Upjohn, Various
•     Date Released: 1957
•     Effective Dose:10-40mgs/day
•     Active life:6-8 hours
•     Detection Time: 2 months
•     Anabolic/Androgenic ratio:1,900/850


Fluoxymesterone is an oral anabolic steroid derived from testosterone. More specifically, it is a methyltestosterone derivative, differing by the addition of 11-beta-hydroxy and 9-alpha-fluoro groups. The result is a potent orally active non-aromatizable steroid that exhibits extremely strong androgenic properties. Fluoxymesterone is considerably more androgenic than testosterone, while at the same time the anabolic effects of this agent are considered to be moderate in comparison. This makes fluoxymesterone a great strength drug, but not the most ideal agent for gaining muscle mass. The predominant effects seen when taking fluoxymesterone are increased strength, increased muscle density, and increased definition, with only modest size increases.


Fluoxymesterone was first described in 1956. It was assayed that same year, and shown to possess approximately 20 times the anabolic potency of methyltestosterone510 (its relative anabolic effect in humans would not be quite as strong in comparison). It was introduced to the U.S. prescription drug market shortly after under the brand name Halotestin (Upjohn), and soon after that as Ultandren (Ciba). The drug was initially described as halogenated derivative of testosterone, possessing up to 5 times greater anabolic and androgenic potency than methyltestosterone. Early prescribing guidelines recommended its use in both sexes for the promotion of lean tissue repair and growth following such conditions as burns, delayed healing of fractures, chronic malnutrition, debilitating diseases, convalescence, paraplegia, and catabolism induced by long-term administration of cortisone. It was also used in males to treat insufficient androgen levels, and in women to treat abnormal bleeding in the uterus and advanced breast cancer.

Structural Characteristics:

Fluoxymesterone is a modified form of testosterone. It differs by 1) the addition of a methyl group at carbon 17-alpha, which helps protect the hormone during oral administration, 2) the introduction of a fluoro group at carbon 9 (alpha) and 3) the attachment of a hydroxyl group at carbon 11 (beta), which inhibits steroid aromatization. The latter two modifications also greatly enhance the androgenic and relative biological activity of the steroid over 17-alpha methyltestosterone.

Side Effects (Estrogenic):

Fluoxymesterone is not aromatized by the body, and is not measurably estrogenic. An anti-estrogen is not necessary when using this steroid, as gynecomastia should not be a concern even among sensitive individuals. Since estrogen is the usual culprit with water retention, this steroid instead produces a lean, quality look to the physique with no fear of excess subcutaneous fluid retention. This makes it a favorable steroid to use during cutting cycles, when water and fat retention are major concerns.

Side Effects (Androgenic):

Fluoxymesterone is classified as an androgen. Androgenic side effects are common with this substance, and may include bouts of oily skin, acne, and body/facial hair growth. Anabolic/androgenic steroids may also aggravate male pattern hair loss. Those genetically prone to male pattern hair loss may wish to opt for a milder, less androgenic, anabolic steroid. As a potent androgen, this steroid may also increase aggressiveness. Women are additionally warned of the potential virilizing effects of anabolic/androgenic steroids. These may include a deepening of the voice, menstrual irregularities, changes in skin texture, facial hair growth, and clitoral enlargement.
Fluoxymesterone appears to be a good substrate for the 5- alpha reductase enzyme. This is evidenced by the fact that a large number of its metabolites are found to be 5-alpha reduced androgens,511 which coupled with its outward androgenic nature, suggests that this steroid is converting to a much more active steroid in androgen responsive target tissues such as the skin, scalp and prostate. It may be possible to reduce the relative androgenicity of fluoxymesterone by the concurrent use of finasteride or dutasteride. It is also of note that fluoxymesterone has been shown to possess usual androgenic properties. In human studies published back in 1961, the steroid displayed a much stronger tendency to promote phallic enlargement compared to other androgenic effects such as hair growth, libido, and changes in vocal pitch. Fluoxymesterone was offering a somewhat different androgenic profile compared to testosterone, and as such demonstrated that it was possible, at some level, to actually tailor drug effect within the broad category of androgenic action. Fluoxymesterone remains considered an androgen, but studies like the above suggest that it may not offer a complete biological equivalent to testosterone where androgenicity is concerned.

Side Effects (Hepatotoxicity):

Fluoxymesterone is a c17-alpha alkylated compound. This alteration protects the drug from deactivation by the liver, allowing a very high percentage of the drug entry into the bloodstream following oral administration. C17-alpha alkylated anabolic/androgenic steroids can be hepatotoxic. Prolonged or high exposure may result in liver damage. In rare instances life-threatening dysfunction may develop. It is advisable to visit a physician periodically during each cycle to monitor liver function and overall health. Intake of c17- alpha alkylated steroids is commonly limited to 6-8 weeks, in an effort to avoid escalating liver strain. Studies administering 20 mg of fluoxymesterone to a group of nine male subjects for two weeks resulted in most patients (6/9) noticing abnormal sulfobromophthalein (BSP) retention, a marker of liver stress.
The use of a liver detoxification supplement such as Liver Stabil, Liv-52, or Essentiale Forte is advised while taking any hepatotoxic anabolic/androgenic steroids.