Peptide Encyclopedia / MK-677
EncyclopediaMK-677, or ibutamoren, is an orally active non-peptide ghrelin-receptor agonist and growth hormone secretagogue that Merck studied but never brought to approval. Human trials raised GH, IGF-1, and lean mass without improving strength, and worsened insulin sensitivity. Educational only, not medical advice.
| Also known as | Ibutamoren, MK-0677, L-163191 |
| Half-life | 24 hours (long-acting |
| Regulatory status | NOT FDA-approved for any indication. |
NOT FDA-approved for any indication. Ibutamoren (MK-677) is an orally active, non-peptide ghrelin-receptor agonist / growth hormone secretagogue investigated by Merck but never approved. It is sold only as an unapproved research chemical and is prohibited in sport; WADA lists growth hormone secretagogues including ibutamoren (MK-677) under Prohibited List section S2.
MK-677 is a potent, long-acting, orally active, non-peptide agonist of the growth hormone secretagogue receptor (GHS-R1a, the ghrelin receptor). By mimicking ghrelin, it stimulates pulsatile growth hormone secretion from the pituitary and increases serum IGF-1. Unlike injectable peptide secretagogues, it is orally bioavailable. Pharmacokinetics (half-life Approximately 24 hours (long-acting; supports once-daily oral dosing). Detailed parameters are from investigational studies, not an FDA label.): MK-677 is orally absorbed and produces sustained elevation of GH and IGF-1 with once-daily dosing. As an unapproved agent there is no FDA-reviewed PK label; the ~24-hour duration of action supporting once-daily oral dosing is described in the published trial literature.
Studied in randomized human trials but never approved. In the Nass 2008 12-month randomized trial in healthy older adults, oral MK-677 increased GH and IGF-1 and increased fat-free mass by ~1.1 kg, but did NOT improve muscle strength or function and worsened insulin sensitivity / raised blood glucose. Evidence shows biochemical and body-composition effects without demonstrated functional benefit, alongside metabolic safety signals. Reported use: Reported (not approved) community use describes a single daily oral dose (commonly cited around 10-25 mg/day), often taken at night. The Nass trial used 25 mg orally once daily. These reflect investigational and community-reported regimens, not an FDA-approved label, and are not validated or prescriptive.
Reported adverse effects include increased appetite, fluid retention/edema, arthralgias, fatigue, and clinically meaningful increases in fasting blood glucose with reduced insulin sensitivity (a notable signal in the Nass trial). There is theoretical concern for promoting growth of occult malignancy via IGF-1 elevation, and concerns about congestive heart failure have been raised in frail populations in related secretagogue research. Product identity/purity is unverified as a research chemical..
Diabetes or impaired glucose tolerance (worsening insulin sensitivity / hyperglycemia), Active or suspected malignancy (theoretical IGF-1-mediated concern), Congestive heart failure (caution/avoid; fluid retention and signals in vulnerable populations), Pregnancy and lactation (not studied).
Antidiabetic medications: may counteract glucose-lowering effects due to increased insulin resistance, Additive GH effects with other GH secretagogues / GHRH analogs, No verified source found for a comprehensive FDA-reviewed interaction profile
PepWise is an informational and educational tracking tool, not medical advice and not a medical device. MK-677 may be experimental, restricted, or prescription-only; many research peptides are not FDA-approved. Consult a licensed healthcare provider before starting, changing, or stopping any protocol. Operated by STC Consulting, Inc.
