Mibolerone is an oral anabolic steroid, structurally derived dimethylated nandrolone. This agent is specifically 7,17-dimethylated nandrolone, significantly more potent as an anabolic and androgenic agent than its non-methylated parent. Over the years, mibolerone has earned a reputation among bodybuilders as being one of the strongest steroids ever made. This is correct in a technical sense, as it is one of only a select few commercial steroid products effective in microgram, not milligram, amounts. During standard animal assays, mibolerone was determined to have 41 times the anabolic activity of methyltestosterone when given orally. In contrast, it had only 18 times the androgenic activity. Although both properties are strongly pronounced with this agent, it retains a primarily anabolic character (in a relative sense). Estrogenic and progestational properties are also very pronounced with this drug, however. Among athletes it is most commonly applied during bulking phases of training, or to stimulate aggression before a workout or competition.
Mibolerone is a modified form of nandrolone. It differs by 1) the addition of a methyl group at carbon 17-alpha to protect the hormone during oral administration and 2) the introduction of a methyl group at carbon 7 (alpha), which inhibits 5-alpha reduction and increases relative androgenicity. 7,17-dimethylated steroids also tend to be very resistant to metabolism and serum-binding proteins, greatly enhancing their relative biological activity.
Studies have shown that taking an oral anabolic steroid with food may decrease its bioavailability.432 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.
Mibolerone was never approved for use in humans. Prescribing guidelines are unavailable. In the athletic arena, the drug is used intermittently due to its high level of hepatotoxicity, with cycles usually lasting no more than 6 weeks followed by 6-8 weeks off. A daily dosage of 200 to 500mcg is most common for bodybuilding purposes. This level is typically sufficient for gains in strength and muscle mass (bulk). The high progestational and estrogenic activity of mibolerone makes it of little value in speed and endurance sports, causing an unwanted retention of water weight.
Mibolerone was never approved for use in humans. Prescribing guidelines are unavailable. Mibolerone is generally not recommended for women for physique- or performance-enhancing purposes due to its very strong nature and tendency to produce virilizing side effects.
Mibolerone is aromatized by the body, and is considered a highly estrogenic steroid due to its conversion to 7,17-dimethylestradiol (an estrogen with high biological activity). Gynecomastia may be a concern during treatment, especially when higher than normal therapeutic doses are used. At the same time water retention can become a problem, causing a notable loss of muscle definition as both subcutaneous water retention and fat levels build. To avoid strong estrogenic side effects, it may be necessary to use an anti-estrogen such as Nolvadex®. One may alternately use an aromatase inhibitor like Arimidex® (anastrozole), which is a more effective remedy for estrogen control. Aromatase inhibitors, however, can be quite expensive in comparison to standard estrogen maintenance therapies, and may also have negative effects on blood lipids.
It is of note that mibolerone also displays strong activity as a progestin in the body. The side effects associated with progesterone are similar to those of estrogen, including negative feedback inhibition of testosterone production and enhanced rate of fat storage. Progestins also augment the stimulatory effect of estrogens on mammary tissue growth. There appears to be a strong synergy between these two hormones here, such that gynecomastia might even occur with the help of progestins without excessive estrogen levels being present. The use of an anti-estrogen, which inhibits the estrogenic component of this disorder, is often sufficient to mitigate gynecomastia caused by mibolerone.
Although classified as an anabolic steroid, androgenic side effects are still common with this substance. This may include bouts of oily skin, acne, and body/facial hair growth. Anabolic/androgenic steroids may also aggravate male pattern hair loss. Individuals sensitive to the androgenic effects of this steroid may find a milder anabolic such as Deca-Durabolin® to be more comfortable. 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. Note that 7-methylation inhibits steroid 5-alpha reduction.431 The relative androgenicity of mibolerone is not affected by the concurrent use of finasteride or dutasteride.
(Source: Anabolics - by Willaim Llewellyn.)