Informational only. Not medical advice.INFORMATIONAL PLATFORM ONLY — NOT MEDICAL ADVICE, DIAGNOSIS, OR TREATMENT
Informational only. Not medical advice.INFORMATIONAL PLATFORM ONLY — NOT MEDICAL ADVICE, DIAGNOSIS, OR TREATMENT
Head-to-head comparison of Capromorelin and MK-677 — mechanism, dosing, side effects, legal status, and pricing.
Capromorelin is a non-peptide, orally active pyrazolinone-piperidine dipeptide-mimetic that functions as a growth hormone secretagogue receptor 1a (GHS-R1a) agonist, mimicking the endogenous hormone ghrelin. It is NOT approved for human use anywhere; a Pfizer Phase II trial in 395 older adults showed positive signals for lean body mass, body weight, and physical function but was terminated early and never advanced to approval. Capromorelin is FDA-approved as a veterinary drug (Entyce for dogs, Elura for cats) and is explicitly named on the WADA Prohibited List under S2 (growth hormone secretagogues), prohibited at all times in competitive sport.
MK-677 (ibutamoren, MK-0677, L-163,191) is an orally active, non-peptide small-molecule growth hormone secretagogue developed by Merck in the 1990s. It is a spiropiperidine ghrelin-receptor (GHSR-1a) agonist — not a peptide and not a SARM, though it is commonly misclassified as both in grey-market retail. Merck discontinued development after mixed efficacy and adverse metabolic / cardiovascular findings; it is not FDA-approved.
Capromorelin
MK-677
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Capromorelin
MK-677
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Capromorelin
No COA data yet.
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5
COAs
98.3%
Avg purity
3
Labs
Capromorelin has human clinical trial data but is not an approved human drug. A Pfizer-sponsored Phase II trial randomized 395 adults aged 65–84 at risk of functional decline to oral capromorelin or placebo for up to 2 years (315 completed 6 months; 284 completed 12 months). The trial reported increased lean body mass (+1.4 vs 0.3 kg, P=0.001), body weight (+1.4 kg, P=0.006), improved tandem walk (P=0.02), and improved stair climb (P=0.04), concluding capromorelin "may improve body composition and physical function." The study was terminated early according to predetermined treatment effect criteria; no human product was ever approved. Preclinical studies in rats showed an ED50 <0.05 mg/kg IV for plasma GH elevation; in healthy Beagle dogs, oral capromorelin increased food consumption and body weight in a 4-day randomized, masked, placebo-controlled trial. In healthy cats, capromorelin altered glucose-metabolism parameters. In broiler chickens, it increased feed intake and body-weight gain.
Key references
MK-677 has meaningful human data from Merck-sponsored Phase I/II trials. Murphy et al. (JCEM 1998, PMID 9467534) showed 25 mg MK-677 reversed nitrogen wasting during caloric restriction in healthy adults. Svensson et al. (JCEM 1998, PMID 9467542) reported ~40% IGF-1 elevation, increased fat-free mass, and higher energy expenditure over 8 weeks in obese men. Copinschi et al. (Neuroendocrinology 1997, PMID 9349662) documented improved slow-wave and REM sleep in young and older adults. Nass et al. (Ann Intern Med 2008, PMID 18981485) — the pivotal 2-year randomized trial in 65 healthy older adults — restored GH and IGF-1 to young-adult levels and increased fat-free mass, but produced modest fasting glucose elevation and insulin resistance. The Adunsky et al. Phase IIb hip-fracture trial (Arch Gerontol Geriatr 2011, PMID 21067829) was stopped early after a congestive-heart-failure safety signal (4/62 ibutamoren vs 1/60 placebo). Merck discontinued development. MK-677 is commonly mislabeled as a 'SARM' in grey-market retail — it is not; it is a ghrelin-receptor agonist and oral GH secretagogue. It has never been FDA-approved.
Capromorelin (Hormone) and MK-677 (Performance) are in different categories and target different biological pathways. This is a common pattern in multi-compound research protocols. Researchers should monitor the biomarkers from both profiles and watch for interactions listed in each compound’s contraindications. Consult a licensed healthcare provider before combining any research compounds.
This platform provides informational tools only, not medical advice. This comparison is for educational purposes only. Consult a licensed provider.
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Key references
Disclosed Labs