Side-by-side comparison of mechanisms, dosing, interactions, and stacking potential.
| MK-677 (Ibutamoren) | SR-9009 (Stenabolic) | |
|---|---|---|
| Category | SARMs | SARMs |
| Standard Dose | Research indicates 10-25 mg daily orally. Clinical trials used 25 mg/day. 10-15 mg may provide GH elevation with fewer side effects. | Research indicates 20-30 mg daily orally, split into 3-4 doses due to very short half-life (~4 hours). Some users prefer sublingual administration for improved bioavailability. |
| Timing | Take 30-60 minutes before bedtime. This timing leverages the natural nocturnal GH pulse, maximizes sleep quality benefits, and minimizes daytime appetite increase. Half-life ~24 hours ensures once-daily dosing is sufficient. | Split into 3-4 doses throughout the day due to ~4-hour half-life. Example: 7am, 11am, 3pm, 7pm. Avoid late-night dosing as REV-ERB modulation may affect circadian rhythm and sleep. |
| Cycle Duration | Can be used continuously for months to years — no cycling required as it works through physiological GH release mechanisms. Clinical trials ran for up to 2 years. Reassess IGF-1 and metabolic markers every 3-6 months. | 8-12 week cycles. No HPG suppression. Cycling recommended due to limited long-term data. |
| Evidence Level | moderate_human | animal_plus_anecdotal |
MK-677 (ibutamoren) is an orally active, non-peptide growth hormone secretagogue that mimics ghrelin by binding the ghrelin receptor (GHSR1a) in the hypothalamus and pituitary. This triggers pulsatile growth hormone release via the same physiological mechanism as endogenous ghrelin, preserving the natural episodic GH secretion pattern. MK-677 increases GH, IGF-1, and IGFBP-3 levels to those observed in young adults without affecting cortisol levels. It also stimulates appetite through ghrelin receptor activation in the hypothalamus. Unlike exogenous GH injection, MK-677 maintains the pulsatile GH pattern and stimulates all five GH isoforms.
Research indicates 10-25 mg daily orally. Clinical trials used 25 mg/day. 10-15 mg may provide GH elevation with fewer side effects.
Take 30-60 minutes before bedtime. This timing leverages the natural nocturnal GH pulse, maximizes sleep quality benefits, and minimizes daytime appetite increase. Half-life ~24 hours ensures once-daily dosing is sufficient.
Can be used continuously for months to years — no cycling required as it works through physiological GH release mechanisms. Clinical trials ran for up to 2 years. Reassess IGF-1 and metabolic markers every 3-6 months.
SR-9009 is a synthetic agonist of REV-ERBa and REV-ERBb, nuclear receptors that form the repressive limb of the circadian clock and regulate metabolic gene expression. REV-ERB activation represses BMAL1/CLOCK transcription, modulating circadian rhythm. In skeletal muscle, SR-9009 increases mitochondrial count and oxidative capacity by upregulating mitochondrial biogenesis genes. It enhances fatty acid and glucose oxidation, increases exercise endurance, and reduces lipogenesis in the liver. SR-9009 also reduces inflammatory gene expression via NF-kB pathway suppression. Recent research has identified significant REV-ERB-independent effects, suggesting the mechanism is more complex than initially characterized.
Research indicates 20-30 mg daily orally, split into 3-4 doses due to very short half-life (~4 hours). Some users prefer sublingual administration for improved bioavailability.
Split into 3-4 doses throughout the day due to ~4-hour half-life. Example: 7am, 11am, 3pm, 7pm. Avoid late-night dosing as REV-ERB modulation may affect circadian rhythm and sleep.
8-12 week cycles. No HPG suppression. Cycling recommended due to limited long-term data.
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