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Phase IIIVendors pendingFacts verified · 2026-05-25

Ibutamoren (MK-677, oral tablets)

Also known as MK-677 (Ibutamoren) (Tablets), ibutamoren mesylate, mk-0677, growth hormone secretagogue · Wikipedia

MK-677 (ibutamoren, MK-0677) is a non-peptide small molecule ghrelin-receptor (GHSR1a) agonist developed by Merck and now sold as an oral research chemical for GH/IGF-1 support, sleep, and body composition. It is not a peptide and is orally bioavailable. It produces sustained elevations of pulsatile GH and IGF-1 with once-daily dosing and is WADA-banned (class S2). Clinical development was discontinued after Phase II/III trials in sarcopenia and hip-fracture populations; a notable hip-fracture trial in elderly patients (Adunsky et al., 2011) was associated with an increased congestive heart failure signal.

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Mechanism of action

MK-677 (ibutamoren mesylate, MK-0677) is a non-peptide small molecule and potent, orally active agonist of the ghrelin receptor (GHS-R1a) on pituitary somatotrophs and hypothalamic neurons. By mimicking endogenous ghrelin's GH-releasing action, it produces sustained elevations in pulsatile GH secretion and downstream IGF-1 with once-daily oral dosing (Patchett et al.

MK-677 (ibutamoren mesylate, MK-0677) is a non-peptide small molecule and potent, orally active agonist of the ghrelin receptor (GHS-R1a) on pituitary somatotrophs and hypothalamic neurons. By mimicking endogenous ghrelin's GH-releasing action, it produces sustained elevations in pulsatile GH secretion and downstream IGF-1 with once-daily oral dosing (Patchett et al., 1995). Unlike peptide GHRPs, it has a long functional duration and high oral bioavailability. Central ghrelin signaling also drives appetite stimulation and weight gain. Adunsky et al. (PubMed 21067829) reported a Phase 2b multicenter randomized placebo-controlled trial in hip-fracture recovery, in which MK-0677 increased IGF-1 but did not yield convincing functional benefit and was associated with a cardiac safety signal.

Pharmacokinetic properties

Half-life

~4-6 hours plasma; functional GH/IGF-1 elevation 18-24 hours (sustained receptor engagement)

Routes

oral

Bioavailability

Orally bioavailable (non-peptide); designed for once-daily dosing. Reaches steady-state IGF-1 elevation within ~1-2 weeks.

Amino-acid sequence

(Not a peptide; non-peptide GHSR1a agonist)

Use & research dosing

GH/IGF-1 SupportSleep QualityBody Composition

Self-experimentation protocols circulating in the research-chemical channel commonly use 10-25 mg orally once daily, often at bedtime to amplify nocturnal GH pulses. Clinical trials in elderly subjects, GH-deficient adults, and hip-fracture and osteoporosis populations have used 10-25 mg/day. Steady-state IGF-1 elevation is typically reached within 1-2 weeks of daily dosing. Not FDA-approved; Merck discontinued development after Phase II/III trials. Research framing only.

Research-use framing only. SavePeptides sells nothing for human consumption. Doses above reflect reported research / self-experimentation ranges, not clinical recommendations.

Editorial perspective

Not a peptide - this is a small-molecule ghrelin mimetic erroneously catalogued alongside peptide products. The most important safety landmine is the Adunsky et al. 2011 hip-fracture trial in elderly patients, which raised a congestive heart failure signal and contributed to the abandonment of clinical development. Insulin resistance, fluid retention, and appetite-driven weight gain are predictable and persistent effects with chronic use. WADA-banned in competitive sport.

— SavePeptides editorial desk · last updated 2026-05-25

Cautions & contraindications

Before researching this compound, note:

  • Not FDA-approved; sold as a research chemical / unscheduled compound (legal status varies by jurisdiction)
  • WADA-banned (class S2) - prohibited in competitive sport at all times
  • Significant appetite stimulation and weight gain (lean plus fat)
  • Fluid retention, peripheral edema, and increased blood pressure are common
  • Insulin resistance and impaired fasting glucose, particularly with chronic higher-dose use
  • Increased congestive heart failure incidence in an elderly hip-fracture trial (Adunsky 2011) - avoid in cardiovascular disease and the frail elderly
  • Avoid in active or suspected malignancy (IGF-1 elevation)
  • Avoid in pregnancy and breastfeeding
  • Drowsiness, lethargy, and vivid dreams are common at higher doses

Research foundation

The papers behind the page.

  1. [01]https://pubmed.ncbi.nlm.nih.gov/21067829/
  2. [02]https://pubmed.ncbi.nlm.nih.gov/9349662/

Facts verified

2026-05-25

Confidence

medium

What this means

  • not a peptide — small molecule or other compound on the marketplace
  • not a peptide - small molecule GHSR1a agonist
  • WADA-banned
  • CHF safety signal in elderly hip-fracture trial
  • incorrect clinical_status in source - corrected to Phase III trials (discontinued)

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Ibutamoren (MK-677, oral tablets) · SavePeptides