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| Other names | MK-677; MK-0677; L-163,191; Oratrope |
| Routes of administration | By mouth |
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| Elimination half-life | 4–6 hours (in beagles); [1] IGF-1 levels remain elevated in humans with a single oral dose for up to 24 hours [2] |
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| ECHA InfoCard | 100.236.734 |
| Chemical and physical data | |
| Formula | C27H36N4O5S |
| Molar mass | 528.67 g·mol−1 |
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Ibutamoren (INN ; developmental code MK-677, MK-0677, LUM-201, L-163,191; former tentative brand name Oratrope) is a potent, long-acting, orally-active, selective, and non-peptide agonist of the ghrelin receptor and a growth hormone secretagogue, mimicking the growth hormone (GH)-stimulating action of the endogenous hormone ghrelin. [3] [4] [5] [6] [7] It has been shown to increase the secretion of several hormones including GH and insulin-like growth factor 1 (IGF-1) and produces sustained increases in the plasma levels of these hormones while also raising cortisol levels. [8]
Ibutamoren has been shown to sustain activation of the GH–IGF-1 axis, increasing growth hormone secretion by up to 97%, [9] and to increase lean body mass with no change in total fat mass or visceral fat. It is under investigation as a potential treatment for reduced levels of these hormones, such as in children or elderly adults with growth hormone deficiency, [3] [10] [11] [12] and human studies have shown it to increase both muscle mass and bone mineral density, [13] [14] making it a promising potential therapy for the treatment of frailty in the elderly. [15] [16] As of June 2017, ibutamoren is in the preclinical stage of development for growth hormone deficiency. [3]
In a small study of 14 subjects, ibutamoren dosed at 25 mg/day at bedtime was shown to increase rapid eye movement sleep by 20% and 50% in young and older subjects respectively. [17] Treatment with ibutamoren also resulted in an approximate 50% increase in slow-wave sleep in young subjects. [17]
In a study of children with growth hormone deficiency, ibutamoren performed better than other growth hormone secretagogues at improving growth hormone levels. [18] An ongoing study compares ibutamoren directly to injectable hGH in terms of height velocity in this population. [19]
Since ibutamoren is still an Investigational New Drug, it has not yet been approved to be marketed for consumption by humans in the United States. [3] However, it has been used experimentally by some in the bodybuilding community. The use of ibutamoren is banned in most sports. [20]