Growth & GHSmall molecule (GH secretagogue)Evidence B4 cited

MK-677

Ibutamoren Mesylate

aka Ibutamoren · MK-0677 · L-163191 · ibutamoren mesylate

An oral ghrelin mimetic that research shows reliably elevates GH and IGF-1 levels.

Molecular wt

528.7 (free base); 624.8 (ibutamoren mesylate, PubChem CID 6450830)g/mol

Formula

C27H36N4O5S (free base). The mesylate salt, which is the form used in the clinical trials, is C28H40N4O8S2.

CAS

159634-47-6 (ibutamoren free base). 159752-10-0 is the CAS number of ibutamoren mesylate.

Half-life

5 h

clinical

Tmax

1 h

Route

Oral

PubChem

178024 (free base); 6450830 (mesylate)

Sequence

Read this before quoting the sequence

NOT A PEPTIDE. MK-677 (ibutamoren) is a synthetic non-peptide small molecule - a spiroindoline/spiropiperidine derivative that acts as an orally active agonist at the ghrelin receptor (GHS-R1a) and thereby as a growth hormone secretagogue. It has no amino acid sequence. Its systematic name is 2-amino-2-methyl-N-[(2R)-1-(1-methylsulfonylspiro[2H-indole-3,4'-piperidine]-1'-yl)-1-oxo-3-phenylmethoxypropan-2-yl]propanamide.

Source ↗

Mechanism of action

MK-677 works by mimicking the hormone ghrelin, binding to the ghrelin receptor in the brain. This stimulates the release of growth hormone (GH) from the pituitary gland. The increase in GH subsequently raises levels of insulin-like growth factor 1 (IGF-1), which plays a role in growth and metabolism.

What the evidence actually shows

Grade B

SAFETY: DEA warning (2025). Cardiac risk — CHF 6.5% vs 1.7% placebo in hip fracture trial. Insulin resistance across trials. Cancer risk via chronic IGF-1. No long-term safety data. WADA banned. FDA found 40% of online products had incorrect dosages.

Regulatory status

Status

Never approved as a medicine in any jurisdiction. Investigational only; development discontinued.

Clinical stage

Reached large randomised trials (n=563 in Alzheimer disease, 12 months; 2-year trial in healthy older adults) but was not carried to approval.

WADA

Prohibited. The WADA Prohibited List section S2.2 names 'growth hormone secretagogues (GHS) and their mimetics [e.g. anamorelin, capromorelin, ibutamoren (MK-677), ipamorelin, lenomorelin]'. Prohibited at all times.

research_compound

In the UK, MK-677 is not approved for medical use and is considered a research compound. It is not licensed for human consumption.

Source ↗

Pharmacokinetics

Half-life

5 h

Tmax

1 h

Absorption

oral

Elimination

hepatic

Washout

14 days

Titration

10mg x1wk then 25mg

Low-confidence pharmacokinetics

These figures are recorded as clinical rather than measured in a published PK study. Treat them as an order of magnitude. Anything downstream of them — accumulation, steady state, washout — inherits that uncertainty.

Dosing — what backs each figure

MK-677 (ibutamoren) was never approved, but unlike most compounds on this page it has real published human trial dosing: 25 mg orally once daily is the regimen used in randomised placebo-controlled studies in healthy older adults (n=65, 2 years) and in Alzheimer disease (n=563, 12 months). Those trials also documented the trade-offs at that dose - raised IGF-1 alongside increased appetite, fluid retention and reduced insulin sensitivity - and none of them cycled the drug.

ClinicalApproved labelling or a published human trial

25 mg orally once daily for 12 months (primary endpoints) within a 2-year double-blind randomised placebo-controlled modified-crossover trial
65 healthy adults aged 60-81 (men, and women with and without HRT) · oral
Nass R et al. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults. Ann Intern Med 2008;149:601-11 ↗
25 mg orally once daily for 12 months
563 patients with mild-to-moderate Alzheimer disease, double-blind multicentre randomised trial · oral
Sevigny JJ et al. Growth hormone secretagogue MK-677: no clinical effect on AD progression in a randomized trial. Neurology 2008;71:1702-8 ↗
LUM-201 (ibutamoren mesylate) 25 mg orally once daily, open-label
12 adults with BMI >=25 and histologic or radiologic NAFLD · oral
ClinicalTrials.gov NCT05364684 (Phase 2, completed) ↗

Handling and storage

No compound-specific stability data exists

Not a lyophilised peptide; storage fields modelled on peptide handling do not apply. No approved product exists, so there is no label storage section, and no peer-reviewed stability data for MK-677 was located. General peptide handling still applies — reconstitute gently, keep it cold, keep it dark — but any specific figure you see quoted for this compound elsewhere is someone's assumption, not a measurement.

→ Reconstitution walkthrough → Reconstitution calculator

Safety

Commonly reported

·Increased appetite
·Mild edema
·Muscle pain

Rarely reported

·Carpal tunnel syndrome
·Insulin resistance

Contraindications

·Pregnancy
·"Active cancer"

Drug interactions

·Insulin: May alter glucose metabolism
·Corticosteroids: Potential additive effects on glucose levels

Increased appetite, water retention, transient insulin resistance, lethargy

Reported combinations

Reported as synergistic

·L-arginine: May enhance GH release

Reported as antagonistic

·Somatostatin analogs: Inhibit GH release

Combination claims in this dataset are largely unsourced and should be treated as folk knowledge until a citation appears beside them.

References (4)

Nass R, Pezzoli SS, Oliveri MC, Patrie JT, Harrell FE, Clasey JL, Heymsfield SB, Bach MA, Vance ML, Thorner MO. (2008) Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults: a randomized trial ↗
Ann Intern MedPMID 18981485DOI
Two-year double-blind randomised placebo-controlled trial in healthy older adults; oral MK-677 raised GH and IGF-1 into the young-adult range and increased fat-free mass, but did not improve strength or function. Some participants developed increased fasting blood glucose and insulin resistance.
Sevigny JJ, Ryan JM, van Dyck CH, Peng Y, Lines CR, Nessly ML; MK-677 Protocol 30 Study Group. (2008) Growth hormone secretagogue MK-677: no clinical effect on AD progression in a randomized trial ↗
NeurologyPMID 19015485DOI
563 patients with mild-to-moderate Alzheimer disease randomised to MK-677 25 mg daily or placebo for 12 months; MK-677 did not slow disease progression. This is the largest published MK-677 trial and it was negative.
Murphy MG, Plunkett LM, Gertz BJ, He W, Wittreich J, Polvino WM, Clemmons DR. (1998) MK-677, an orally active growth hormone secretagogue, reverses diet-induced catabolism ↗
J Clin Endocrinol MetabPMID 9467534DOI
Randomised clinical study showing oral MK-677 reversed nitrogen wasting during short-term dietary restriction in healthy volunteers.
Cobani E, Amin MS, Hasso M, Kumbar L. (2025) Hepatotoxicity induced by MK-677 ↗
BMJ Case RepPMID 40675653DOI
Case report: an otherwise healthy man in his early 30s developed transaminitis after two months of non-prescription MK-677 use; liver function normalised after stopping. Documented safety signal beyond the labelled trial side effects of oedema, increased appetite and muscle pain.

Data provenance

Chemistry and citations on this page were checked against primary sources on 2026-08-14. Values that could not be verified were left blank rather than filled with a plausible guess.

Could not verify
storage.lyophilized, storage.reconstituted, storage.lightSensitive

Research use only

This profile is educational reference material. It is not medical advice, not a prescription, and not an endorsement of self-administration. Compounds discussed here are research chemicals and most are not approved for human therapeutic use.

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