MK-677 (Ibutamoren)
Ibutamoren · MK677 · MK 677 · Nutrobal
Orally active growth hormone secretagogue (ghrelin receptor agonist) that elevates GH and IGF-1; the non-peptide counterpart to injectable GHRPs.
Key takeaways
- Oral ghrelin-receptor agonist that raises GH and IGF-1 without injections.
- Half-life ~5 hours, but IGF-1 stays elevated 24 hours, so once-daily dosing works.
- Backed by real randomized human trials (up to 12 months), rare for this class, but no approval.
- Expect increased appetite, water retention, and elevated fasting glucose.
Overview
What it is
MK-677 (ibutamoren) is an orally active, non-peptide ghrelin receptor agonist that elevates growth hormone and IGF-1 around the clock. It delivers GHRP-class signaling without injections, which is most of its appeal.
Pharmacokinetics
The parent half-life is roughly five hours with around 60% oral bioavailability, but the IGF-1 elevation it produces persists far longer, so once-daily dosing is standard in both trials and community use.
What the evidence says
MK-677 has deeper human data than most secretagogues: randomized trials in older adults and GH-deficient patients showed sustained IGF-1 increases and lean mass gains. It was never approved. Increased appetite, water retention, and elevated fasting glucose are consistent findings, and long-term safety data is limited.
Reported dosing protocols
Protocols reported in research literature and clinic/community use — informational context, not a dosing recommendation.
| Use case | Dose | Route | Frequency | Duration |
|---|---|---|---|---|
| GH/IGF-1 elevation (trial dose) | 25 mg | Oral | Once daily | 8 weeks–12 months in published trials |
| Appetite / recovery (community) | 10–15 mg | Oral | Once daily | 8–16 weeks |
Pharmacokinetic summary
- Model tier
- Simple (t½ + F, Tmax estimated)
- Half-life
- 5 hours
- Bioavailability
- 60%
- Typical dose
- 10–25 mg
Frequently asked questions
Is MK-677 a SARM or a peptide?
Neither. It's a small-molecule ghrelin receptor agonist that stimulates your own GH and IGF-1 release. It doesn't bind androgen receptors, and because it isn't a peptide it survives digestion and works orally.
Why is MK-677 taken once daily if the half-life is 5 hours?
The parent compound clears in hours, but the GH pulses it triggers keep IGF-1 elevated across 24 hours. Trials measured sustained IGF-1 increases with single daily dosing, so there's no pharmacokinetic case for splitting doses.
What are the real risks of MK-677?
The consistent trial findings are increased appetite, transient water retention, and higher fasting blood glucose, a genuine concern for anyone insulin-resistant. Safety beyond 12 months is unknown, and chronic GH/IGF-1 elevation carries theoretical cancer-promotion concerns.
References
- Nass et al. (PMC2757071) + DrugBank — Orally-active non-peptide GH secretagogue; parent half-life ~4-6h, terminal ~24h. Bioavailability ~60%.
- Nass et al., Ann Intern Med 2008 — 12-month RCT of MK-677 in healthy older adults — 25 mg/day raised IGF-1 and lean mass; appetite increase and glucose effects noted.
- DrugBank — Ibutamoren (MK-677) — Parent half-life 4–6 h with a ~24 h terminal phase; oral bioavailability ~60%.
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