Ipamorelin vs MK-677: evidence, safety and FDA status
PepsRadar · Comparison · AI-assisted, written from the checked facts on each profile · Content updated (how dates work) · Not reviewed by a medical professional
The short answer
Both push the body to release more growth hormone through the ghrelin receptor, and neither is FDA-approved. Ipamorelin is a peptide; MK-677 (ibutamoren) is a small molecule taken by mouth in its trials, not a peptide. MK-677 has more human data, and it is not reassuring.
Key differences
MK-677 trials in older adults raised fat-free mass and IGF-1, but strength and most physical function did not improve.
MK-677 raised fasting blood sugar and lowered insulin sensitivity, and a hip-fracture trial stopped early over a heart-failure signal.
Ipamorelin’s one randomized trial (after bowel surgery, given intravenously) did not show a significant benefit; FDA notes serious events including a death in that program.
Ipamorelin was developed as a growth-hormone secretagogue. Its often-cited selectivity comes from early pharmacology experiments, not a comprehensive human safety program.
MK-677, or ibutamoren, is a small-molecule ghrelin mimetic. A trial in older adults found increased fat-free mass without an improvement in strength or physical function.
Human evidence
1 randomized trial
2 randomized trials
Human safety data
Trials only. Ipamorelin is an unapproved growth-hormone secretagogue. One surgical trial found adverse events similar to placebo, but FDA notes a published report of serious events, including death, with intravenous use.
Trials only. Investigational growth-hormone secretagogue, not FDA-approved. Trials found raised blood sugar and swelling, and one stopped early over a heart-failure signal; FDA flags significant safety risks.
Boxed warning
No FDA label to carry one
No FDA label to carry one
Serious risks
FDA: serious adverse events including death reported in a study of intravenous ipamorelin for gut motility
Partly supported: Peptides like CJC-1295/ipamorelin are a safe, natural way to boost growth hormone.
Partly supported: MK-677 safely raises growth hormone and builds muscle.
Each row comes from the Ipamorelin and MK-677 profiles, where every fact links to its source. “Conditions flagged” lists the health conditions each profile’s Risks & interactions section mentions.
The human studies
Ipamorelin
Postoperative ileus proof-of-concept trial (2014)
Human randomized trial · 117 patients enrolled after bowel resection; 114 in the safety and modified intention-to-treat populations.
Median time to tolerating a standardized meal was 25.3 hours with ipamorelin and 32.6 hours with placebo (p=0.15). Key and secondary efficacy analyses did not show significant between-group differences.
Limitation: Small proof-of-concept study with varied underlying conditions. This setting, route, and endpoint do not test muscle gain, fat loss, sleep improvement, or long-term use.
Human randomized trial · 65 healthy adults aged 60–81.
Fat-free mass increased with ibutamoren versus placebo, but strength and function did not improve. Fasting glucose increased and insulin sensitivity decreased.
Limitation: More fat-free mass does not establish stronger muscles, improved independence, or a longevity benefit.
Human phase 2 randomized trial · 123 older patients recovering from hip fracture.
IGF-1 increased, but most functional measures did not improve. Gait speed improved while the stair-climbing difference was not statistically significant. A congestive-heart-failure safety signal led to early termination.
Limitation: Early stopping limits inference. The safety signal concerns this vulnerable population and cannot quantify risk in healthy users. This small molecule is not a peptide, and the study does not establish safe recreational use.
Results from different trials are not a head-to-head comparison: the people, preparations, durations and measures differ.
Bottom line
More growth hormone has not translated into more strength in these trials, and both carry safety signals worth reading before anything else.
PepsRadar does not give doses or usage instructions, and this page is not medical advice. For a prescription medicine, talk to your prescriber or pharmacist.
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