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 MK-677 and PT-141 — mechanism, dosing, side effects, legal status, and pricing.
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.
PT-141 (bremelanotide) is a cyclic heptapeptide melanocortin receptor agonist derived from melanotan II. It is FDA-approved as Vyleesi (2019) for hypoactive sexual desire disorder (HSDD) in premenopausal women only. It acts centrally through the melanocortin system rather than on peripheral vasculature.
MK-677
PT-141
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MK-677
No pricing data yet.
Check MK-677 prices →PT-141
COA corpus from Disclosed Labs — independently tested batches only.
MK-677
5
COAs
98.3%
Avg purity
3
Labs
PT-141
83
COAs
99.7%
Avg purity
14
Labs
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.
Key references
Bremelanotide received FDA approval in June 2019 (NDA 210557) based on the two Phase III RECONNECT trials reported by Kingsberg, Simon, Clayton, Portman et al. in Obstet Gynecol 2019 (PMID 31599840). Pooled 24-week data showed statistically significant increases in the Female Sexual Function Index desire domain and decreases in the Female Sexual Distress Scale compared with placebo, with long-term 52-week open-label safety reported in the companion paper (PMID 31599847). Earlier clinical programs in men with erectile dysfunction — including intranasal bremelanotide and the subcutaneous sildenafil-salvage study by Safarinejad & Hosseini (J Urol 2008, PMID 18206919) — showed modest efficacy but did not lead to approval in men. Safety monitoring shows transient SBP elevation (~6 mmHg) with reflex bradycardia resolving within ~12 hours; nausea (~40%) is the most common adverse event and typically diminishes with subsequent doses. Focal hyperpigmentation has been reported with repeated use, consistent with MC1R activity.
MK-677 (Performance) and PT-141 (Hormone) 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.
Dosing Notes
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Disclosed Labs