HomePeptides › MK-677

MK-677

Ibutamoren, Ibutamoren mesylate, MK-0677

Tier 3 · Limited Human DataNot a peptide
Class
Orally active growth hormone secretagogue
Molecular target
GHS-R1a (ghrelin receptor)
Sequence / structure
Not applicable — small molecule
Evidence tier
Tier 3 — Limited Human Data
Category
Growth Hormone Axis
Emergency card
Signs something is wrong

Puffiness and fluid retention in the hands and feet, joint aches, wrist tingling (carpal tunnel), and blood sugar creeping up over weeks — most pronounced with MK-677 and somatropin.

What to do now

These accumulate rather than strike suddenly — reassess and stop rather than pushing the dose up. Check glucose if you can.

When it is an emergency

A severe persistent headache with vision changes (possible raised intracranial pressure), or symptoms of very high blood sugar — extreme thirst, confusion, vomiting — warrant urgent care.

Any injection — every time

Allergic reaction: hives, swelling of the lips, tongue or throat, wheezing or dizziness can escalate to anaphylaxis within minutes — call 911 immediately. Site infection: spreading redness, heat, swelling, pus or fever is not wait-and-see; an abscess or cellulitis can need drainage or IV antibiotics. Unverified product: grey-market vials are frequently mislabelled or contaminated, so a reaction may be to endotoxin or the wrong contents, not the named compound.

This is not permission or instruction to use this compound. It is harm-reduction information for someone who has already decided to, so that a bad reaction is recognised and treated. When in doubt, get help — embarrassment is survivable.
This is not a peptideA non-peptide small molecule. It is grouped with peptides commercially and sold by the same vendors, but it is a spiropiperidine, not an amino acid chain.

Biology & mechanism

A small-molecule ghrelin receptor agonist that is orally bioavailable — the reason it is grouped with the injectable GHRPs despite sharing none of their chemistry. It raises GH and IGF-1 in a sustained rather than pulsatile fashion, and its long half-life means the elevation persists around the clock.

What the research actually shows

Better human data than most of this category. Merck developed it through multiple trials, including a two-year study in older adults showing sustained IGF-1 elevation and increased lean mass. Development was ultimately abandoned. A trial in hip-fracture rehabilitation was discontinued after congestive heart failure signals.

Regulatory status

Not FDA-approved. Never approved anywhere. Not a lawful dietary supplement — FDA has issued warning letters to companies marketing it as one. Prohibited in sport (WADA S2).

Safety signals

The signals here are concrete rather than theoretical. Trials reported increased fasting glucose and reduced insulin sensitivity, oedema, arthralgia, and an increase in congestive heart failure in one older-adult population. Sustained appetite stimulation is pronounced. The abandoned development programme reflects these findings, not a lack of interest.

Clinical trial dosing — what the studies actually used

Studied at 25 mg once daily, oral, in Merck trials including a two-year older-adult study. Never approved — the same trials surfaced raised blood glucose and, in one population, increased heart failure.

Reported from clinical trials or FDA labelling as a matter of record. It is not a recommendation, and for unapproved compounds no dose has been shown safe or effective in humans.

We report study doses, not protocols

Above is what was administered in trials or on FDA labels, reported as fact. We do not convert it into a personal protocol, calculate a dose for your body weight, or tell you what to inject or how to reconstitute it — that decision belongs with a licensed physician. See our editorial policy.

References & further reading

Regulatory status changes. This page reflects our reading of public sources as of July 2026 and should be independently verified before it is relied upon.

Important notice Forge Bioenergy publishes scientific reference information only. Nothing on this site is medical advice, a therapeutic claim, or a recommendation to use any substance in humans. Many peptides described here are not approved by the FDA for any use, and several are approved only for narrow indications under prescription. We do not publish dosing, administration, or usage protocols. Consult a licensed physician before making any medical decision.