MK-677
Also known as: Ibutamoren, MK-0677, L-163,191
Molecular Identifiers
Overview
Oral non-peptidic ghrelin receptor (GHS-R1a) agonist that promotes sustained GH and IGF-1 secretion. Unlike GHRP peptides, it is orally bioavailable with a long half-life, maintaining elevated GH levels for up to 24 hours.
The main clinical appeal of MK-677 (ibutamoren) is the sustained elevation of GH and IGF-1 over 24 hours with oral administration, without injections and with amplified pulses that mimic the physiological pattern. Sought effects include muscle mass gain, deeper sleep, increased appetite, and recovery support. Water retention, elevated blood glucose, and paresthesias are relevant limitations.
Technically not a peptide but a non-peptidic small molecule frequently categorized alongside research peptides. It has no regulatory approval from the FDA, EMA, or ANVISA — it was clinically investigated for sarcopenia and frailty, without reaching the market. Today it is prescribed off-label through compounding pharmacies or obtained on the research market, in capsules taken before bedtime. WADA lists it as a substance prohibited in competition.
Within the GH secretagogue landscape, MK-677 is the only oral, long-acting option: it acts on the same GHS-R1a receptor as the GHRPs (ipamorelin, GHRP-2, GHRP-6, hexarelin) but with a ~24-hour half-life rather than short injectable pulses. It also differs from GHRH analogs (sermorelin, CJC-1295, tesamorelin), which engage a different receptor — and could in theory be combined with one of them. In practice, the tonic 24-hour elevation of GH and IGF-1 resembles the CJC-1295 with DAC profile more than the physiological pulses of sermorelin or Mod GRF 1-29.
Small non-peptidic molecule. Oral ghrelin receptor agonist.
Half-life
~24 hours
Administration Route
Oral
Category
GH Secretagogues
Mechanism of Action
- Oral ghrelin receptor (GHS-R1a) agonism
- Sustained GH secretion for 24 hours
- Elevation of serum IGF-1
- Mimicry of physiological GH pattern (amplified pulses)
- Appetite increase via ghrelin signaling
Dosage Protocol
Data compiled from the literature. This does not constitute medical advice.
| Parameter | Value |
|---|---|
| Dose | 10-25 mg per dose |
| Frequency | Once daily |
| Timing | Before bedtime (to minimize GH effects on sleep) |
| Duration | 8-12 weeks |
Reported Side Effects
Adverse effects described in the literature. Severity and frequency vary between individuals.
- Increased appetite (very common)
- Water retention
- Numbness/tingling
- Elevated blood glucose
- Lethargy
- Joint pain
Product Properties
| Purity | >99% |
| Appearance | White capsules or tablets |
| Solubility | Soluble in DMSO, ethanol, and PEG-400 |
| Source | Chemical synthesis |
| Storage | Room temperature (15-25°C) in a dry place for up to 2 years. Protect from moisture and direct light. |
Presentations & Preparation
Vials of MK-677 found in the research market:
Reconstitution
- Diluent: N/A (capsules or tablets)
- Volume: N/A
- Supplied as capsules or tablets
- Administer with or without food
Storage
- Lyophilized: Room temperature
- Reconstituted: N/A
- Keep in a dry place
- Protect from light and moisture
Scientific Studies
Published studies on MK-677.
Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults - a randomized trial
Nass R, Pezzoli SS, Oliveri MC, Patrie JT, Harrell FE Jr, Clasey JL, Heymsfield SB, Bach MA, Vance ML, Thorner MO
Oral administration of the growth hormone secretagogue MK-677 increases markers of bone turnover in healthy and functionally impaired elderly adults
Murphy MG, Bach MA, Plotkin D, Bolognese J, Ng J, Krupa D, Cerchio K, Gertz BJ
Related Peptides
CJC-1295 with DAC
1-2 mg per week · Once per week
CJC-1295 sem DAC
100-200 mcg per injection · 2-3 times daily
GHRP-2
100-300 mcg per injection · 2-3 times per day
GHRP-6
100-300 mcg per injection · 2-3 times per day
Hexarelin
200-300 mcg per injection · 2-3 times per day
Ipamorelin
200-300 mcg per injection · 2-3 times daily