Standard Methyltestosterone (oral)
Chemical Names 9a-fluoro-11b,17b-dihydroxy-17a-methyl-4-androsten-3-one, 9a-fluoro-11b-hydroxy-17a-methyltestosterone
Estrogenic Activity none
Progestational Activity no data available (low)
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 1956.509 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.
By the mid-1970’s, the FDA had been granted much more control over the U.S. drug market. One of the first major changes with steroid medicine came when the FDA required strong substantiation for each potential use of a drug. The prescribing guidelines for fluoxymesterone were soon refined to state that the drug was “effective” for treating various forms of androgen deficiency in males, and reducing the severity of postpartum breast pain and treating androgen-responsive inoperable breast cancer in females. It was also listed as “probably effective” in treating postmenopausal osteoporosis. Current prescribing guidelines for fluoxymesterone list only the uses of treating androgen deficiency in males and breast cancer in females.
In recent years, fluoxymesterone has become viewed more and more as a controversial medication in the eyes of most clinicians. Its hepatotoxicity and potential negative impact of lipids and cardiovascular risk factors are often cited as reasons for avoiding the use of this agent in otherwise healthy males for treating androgen insufficiency. Today, testosterone preparations (injections, gels, patches, implants, etc.) are preferred for this purpose, and they supplement the same androgens missing from the body (testosterone, DHT), not more toxic synthetic derivatives. Fluoxymesterone remains for sale in the U.S. as a generic drug only. It remains available in only limited supply outside of the United States.
Fluoxymesterone is available in select human drug markets. Composition and dosage may vary by country and manufacturer,although generally contain 2mg, 2.5 mg, 5 mg, or 10 mg per tablet.
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 Halotestin 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.512 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,513 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.
Side Effects (Cardiovascular):
Anabolic/androgenic steroids can have deleterious effects on serum cholesterol. This includes a tendency to reduce HDL (good) cholesterol values and increase LDL (bad) cholesterol values, which may shift the HDL to LDL balance in a direction that favors greater risk of arteriosclerosis. The relative impact of an anabolic/androgenic steroid on serum lipids is dependant on the dose, route of administration (oral vs. injectable), type of steroid (aromatizable or non-aromatizable), and level of resistance to hepatic metabolism. Fluoxymesterone has a strong effect on the hepatic management of cholesterol due to its structural resistance to liver breakdown and route of administration. Anabolic/androgenic steroids may also adversely affect blood pressure and triglycerides, reduce endothelial relaxation, and support left ventricular hypertrophy, all potentially increasing the risk of cardiovascular disease and myocardial infarction.
To help reduce cardiovascular strain it is advised to maintain an active cardiovascular exercise program and minimize the intake of saturated fats, cholesterol, and simple carbohydrates at all times during active AAS administration. Supplementing with fish oils (4 grams per day) and a natural cholesterol/antioxidant formula such as Lipid Stabil or a product with comparable ingredients is also recommended.
Side Effects (Testosterone Suppression):
All anabolic/androgenic steroids when taken in doses sufficient to promote muscle gain are expected to suppress endogenous testosterone production. Without the intervention of testosterone-stimulating substances, testosterone levels should return to normal within 1-4 months of drug secession. Note that prolonged hypogonadotrophic hypogonadism can develop secondary to steroid abuse, necessitating medical intervention.
Studies administering 10 mg, 20 mg, or 30 mg of fluoxymesterone to nine healthy male subjects for up to 12 weeks have demonstrated the strong suppression of endogenous testosterone levels, with inconsistent effects on gonadotropin levels. Although not fully understood, fluoxymesterone is proposed to have a direct suppressive effect on testicular steroidogenesis that is not mediated by the suppression gonadotropins.514
The above side effects are not inclusive. For more detailed discussion of potential side effects, see the Steroid Side Effects page.
Studies have shown that taking an oral anabolic steroid with food may decrease its bioavailability.515 This is caused by the fat-soluble nature of steroid hormones, which can allow some of the drug to dissolve with undigested dietary fat, reducing its absorption from the gastrointestinal tract. For maximum utilization, this steroid should be taken on an empty stomach.
To treat androgen insufficiency, early prescribing guidelines for Halotestin called for a dose of 2-10 mg per day. Modern prescribing guidelines call for a daily dosage of 5-20 mg. Therapy is usually initiated at the full 20 mg dosage,which is later adjusted downward to meet the individual needs of the patient. The drug would be continued long-term unless laboratory tests (lipids, liver enzymes, etc.) or side effects contraindicate its continued use. For physique- or performance-enhancing purposes, an effective oral daily dosage would fall in the range of 10-40 mg, taken in cycles lasting no more than 6-8 weeks to minimize hepatotoxicity. This level is sufficient for measurable increases in muscle strength, which may be accompanied by modest increases in lean muscle mass.
Halotestin is commonly used by athletes in weight-restricted sports like wrestling, powerlifting, and boxing, due to the fact that strength gained from the drug is usually not accompanied by great increases in bodyweight. When properly used, it can allow a competitor to stay within a specified weight range, yet drastically improve his performance. Fluoxymesterone is also commonly used for bodybuilding contest preparation. When the competitor has an acceptably low body fat percentage, the strong androgen level (in absence of excess estrogen) can elicit an extremely hard and defined (“ripped”) look to the muscles. The shift in androgen/estrogen ratio additionally seems to bring about a state in which the body may be more inclined to burn off excess fat and prevent new fat storage. The “hardening” effect of fluoxymesterone would, therefore, be somewhat similar to that seen with trenbolone, although it will be without the same level of mass gain.
In cutting phases, a milder anabolic such as Deca-Durabolin® or Equipoise® is commonly stacked with fluoxymesterone, as they provide good anabolic effect without excessive estrogen buildup. Here, fluoxymesterone provides a well-needed androgenic component, helping to promote a more solid and defined gain in muscle mass, with less interference with energy and libido, than might be obtained with a primarily anabolic agent alone. Perhaps Primobolan®-Depot would be an even better choice, as with such a combination there is no buildup of estrogen, and likewise even less worry of water and fat retention. For mass, one might alternately use an injectable testosterone. A mix of 400 mg per week of testosterone enanthate and 20-30 mg daily of fluoxymesterone, for example, often provides exceptional increases in strength and lean muscle mass. A more significant level of androgenic side effects usually accompanies such a combination, however, as both compounds exhibit strong androgenic activity in the body.
Halotestin is most often used as a secondary medication during inoperable androgen-sensitive breast cancer, when other therapies have failed to produce a desirable effect. The dosage used for this application is 10-40 mg per day. Virilizing effects are common at doses of only 10-15 mg per day in these patients. Fluoxymesterone is not recommended for women for physique- or performance-enhancing purposes due to its strong androgenic nature and tendency to produce virilizing side effects.
Pharmaceutical preparations containing fluoxymesterone remain scarce. The drug has largely associated with western medical markets, where it has been falling out of favor for most clinical application. The bulk of the supply presently comes from underground steroid manufacturers.
509. Herr, M E, Hogg J A, Levin R H, J Am Chem Soc. 78, 500 (1956).
510. Lyster S C, Lund G H, and Stafford R O, Endocrinology 58, 781 (1956).
511. Testing for fluoxymesterone (Halotestin®) administration to man: Identification of urinary metabolites by gas chromatography-mass spectrometry. Kammerer R, Mardink J, Jangels M et al. J Steroid Biochem 36 (1990):659-66.
512. Eisenberg, E. Modern Trends in Endocrinology (H. Gardiner-Hill, ed) p 46. Hoeber, NY (1961)
513. Methyltestosterone, related steroids, and liver function. deLorimier A,Gilbert G. et al. Arch Intern Med v116 (1965):289-94.
514. The effects of fluoxymesterone administration on testicular function. Jones TM, Fang VS et al. J Clin Endocrinol Metab 1977 Jan;44(1):121-9.
515. Anabolic Steroids and Sports Volume II. James E. Wright. Sports Science CEnsultants, Natick, MA 1982.