MK-677 (Ibutamoren)

Overview

MK-677 (ibutamoren, also written MK-0677) is an orally active, non-peptide small molecule, not a peptide. It works as a ghrelin-receptor agonist, which prompts the pituitary to release more growth hormone, and in turn raises circulating IGF-1. In a 2-year trial in healthy older adults, a 25 mg once-daily oral dose increased 24-hour mean GH and IGF-1 and added modest fat-free mass, though without measurable gains in strength or physical function.

It is not FDA-approved for any use. Merck investigated it across several programs, including body composition in aging, hip-fracture recovery, and Alzheimer's disease, but it was never brought to market. The Alzheimer's trial raised IGF-1 as expected yet failed to slow disease progression, and a hip-fracture trial was stopped early over a heart-failure safety signal. It is widely used in bodybuilding, but that use is not clinically validated.

Dosing

Every published human trial of MK-677 used a single oral dose of 25 mg once daily. Because it is not FDA-approved, there is no prescribing dose; that figure describes what was studied, not a recommendation.

Side effects

The trials reported increased appetite, water retention, and fatigue, along with higher fasting glucose and reduced insulin sensitivity. A hip-fracture trial was stopped early over a heart-failure signal.

Storage

MK-677 is typically handled as an oral capsule or solution. Follow the supplier's storage guidance, keeping it cool, dry, and away from light. See the full storage & safety guide for handling and disposal basics.