Ibutamoren Mesylate — MK-677, MK-0677, L-163,191

Ibutamoren, also commonly known by its research designation MK-677, is a growth hormone secretagogue. More specifically, it belongs to the GHRP (Growth Hormone Releasing Peptides) class. These drugs all mimic the activity of ghrelin on the growth hormone secretagogue receptor la (GHSRIa), which stimulates the pulsatile secretion of this hormone from the pituitary. Ibutamoren is considered a third generation GHRP, mostly for its refined oral bioavailability. In human studies, it has been shown to significantly elevate serum GH and IGF-1 levels in both the young and elderly, increase fat-free mass and energy expenditure, improve sleep quality, and reduce diet-induced catabolism. In the fitness community, this drug is most commonly used for muscle gain and fat loss, as well as an appetite stimulant. The activity profile of ibutamoren would be most closely compared to that of GHRP-6. Both drugs are potent stimulators of growth hormone release. However, neither is selective for this activity. As with GHRP-6, ibutamoren is likely to also result in mild increases in ACTH (adrenocorticotropic hormone), cortisol, and prolactin levels. Related spillover side effects are always possible, though not especially common or noteworthy with this drug. In most cases the spillover increases in these other hormones are modest, and not outwardly noticeable to the user. Ibutamoren is also a moderately strong appetite stimulant. Be aware that unless diet is controlled, the use of this drug may coincide with a significant increase in daily caloric intake. When diet is controlled, its GH-stimulating properties may support fat loss.

Brand name Ibutamoren Mesylate — MK-677, MK-0677, L-163,191

Ibutamoren Mesylate Key Points

  • Moderate/Strong effect on Appetite
  • Moderate Effect on GH
  • Mild Elevations in Cortisol
  • Mild Elevations in Prolactin

Ibutamoren Mesylate History

Ibutamoren was first described in 1995 by Patchett et al. It was developed during research into novel spiropiperidine derivatives. A series of these compounds had been synthesized and assessed for structure/activity relationship as GHRPs. During these experiments, the researchers specifically sought to "optimize each structural component" of an intermediary molecule of great interest, and develop a drug with high oral and therapeutic efficacy. The final result was ibutamoren. Among the common representatives of the GHRP category, it stands out as the most orally active and viable.

Ibutamoren has been under investigation as a pharmaceutical by Merck. The company actually pushed the drug into early human clinical trials, examining its effect on such conditions such as fibromyalgia, muscular atrophy, Alzheimer's disease, fracture, postmenopausal osteoporosis, and growth hormone deficiency. The studies thus far have found the drug to be well tolerated. While not all clinical endpoints were successfully met during these studies, it did consistently elevate serum IGF-I. Further, it does appear there could be some therapeutic value. However, full clinical trials were never completed. Merck may have abandoned it. Likewise, the future of ibutamoren is unclear at this time.

Ibutamoren is on the World Anti-Doping Agency's (WADA) list of prohibited substances. Screening for this drug began on a large scale during the 2014 Winter Olympics in Sochi. It is now detectable, at least for a short window after use, during routine urine analysis. A blood sample is not required.

Structural Characteristics of Ibutamoren Mesylate

Ibutamoren is a synthetic nonpeptide spiropiperidine with chemical name 2-amino-2-methyl-N-[(2R)-1-(1-methylsulfonylspiro[2H-indole-3,4'-piperidine]-1 ’-yl)-1-oxo-3-pheny I methoxypropan-2-y I] propanamide mesylate. It has a remarkably high level of oral bioavailability, and a prolonged half-life and window of action compared to most other GHRPs, which allows it to be efficacious with once daily administration.

Ibutamoren Mesylate Warnings

Ibutamoren is an unapproved new drug. A thorough understanding of its safety and propensity for side effects in humans is lacking at this time.

This drug should be used with care in epileptic patients. Obesity, uncontrolled hypothyroidism, hyperglycemia, or elevated plasma fatty acids may impair the effectiveness of ibutamoren. This drug should never be used during pregnancy, with cancer, a history of cancer, diabetic retinopathy, sclerosing diseases of the liver or lungs, intracranial hypertension, or uncontrolled diabetes.

How is Ibutamoren Mesylate Supplied

Ibutamoren is available as a research compound or gray market supplement only. It is most commonly prepared in capsules of 25 mg, and oral solutions of 25 mg/mL.

Ibutamoren Mesylate Side Effects (General)

The most common side effects to ibutamoren are an increase in appetite and sleepiness. Also frequently reported are adverse effects typically associated with other types of growth hormone therapy, such as water retention (edema), joint pain (arthralgias), carpal tunnel syndrome, and numbness or tingling in the extremities. Note that the incidence of side effects tends to be lower with GHRP therapy as compared to traditional hGH. This is because GH/IGF-1 release is subject to endogenous synthesis, and as such the drug is less amenable to overdosing.

Ibutamoren Mesylate Side Effects (Impaired glucose tolerance)

Ibutamoren may reduce insulin sensitivity and raise blood sugar levels. This may occur in individuals without preexisting diabetes or impaired glucose tolerance.

Ibutamoren Mesylate Administration

Ibutamoren is given orally. This substance has not been approved for use in humans. Prescribing guidelines are unavailable.

When used for physique- or performance-enhancing purposes, ibutamoren appears to exhibit its optimum efficacy at a dosage of 10-25 mg daily. This is taken in one dose before sleep. Cycles usually last 3-4 months, though programs of 6 months or longer are not uncommon.

Ibutamoren Mesylate Combination Therapy

Ibutamoren (a GHRP) may be combined with a drug from the GHRH (Growth Hormone Releasing Hormone) class, such as sermorelin or CJC-1295. These two drug types alter GH release through two distinct and complimentary mechanisms. Such combination therapy tends to produce substantial synergy with regard to GH release, producing maximum GH elevations that are unobtainable with either drug alone.

Ibutamoren Mesylate Availability

Ibutamoren is not available as a prescription drug product. It is sold exclusively as a "research compound" or gray market supplement. Note that the quality of gray market products can be difficult to assure.


Wlliam Llewellyn (2017) - Anabolics

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