MK-677 vs Ipamorelin: FDA Status and Evidence
Two growth hormone secretagogues compared on FDA status and evidence. Educational only.
Medically reviewed by Charles Kamen, MD, board-certified neurologist ·
MK-677 (ibutamoren) and ipamorelin can both affect growth-hormone signaling, but they are different compounds. MK-677 is an oral small molecule; ipamorelin is an injectable peptide.
Neither is FDA-approved. FDA lists ibutamoren mesylate in Category 2 for both 503A and 503B compounding, and ipamorelin acetate in Category 2 for 503B outsourcing facilities. This page explains the status and the research. It is not an offer to prescribe or supply either one.
| MK-677 | Ipamorelin | |
|---|---|---|
| What it is | Oral small molecule (ghrelin mimetic), not a peptide | Injectable growth hormone releasing peptide |
| FDA approval | Not FDA-approved | Not FDA-approved |
| FDA compounding status | Category 2 for 503A and 503B | Category 2 for 503B; not on the 503A bulks list |
| Best human evidence | 12-month trial in older adults: more lean mass, higher fasting glucose (Nass, 2008) | Phase 2 surgical trial: no clear benefit over placebo (Beck, 2014) |
| Anti-doping status | WADA prohibited | WADA prohibited |
The practical answer: Neither compound is FDA-approved, and FDA has placed both in Category 2 for compounding. Neither has outcome trials supporting anti-aging or body-composition use.
Questions people ask
Is MK-677 or ipamorelin FDA-approved?
No. Neither is FDA-approved for any use.
Is MK-677 a peptide?
No. MK-677 (ibutamoren) is an oral small molecule that acts on the ghrelin receptor. It is often sold alongside peptides.
What does Category 2 mean?
Category 2 is FDA's list of bulk drug substances that may present significant safety risks in compounding. FDA lists ibutamoren mesylate there for 503A and 503B, and ipamorelin acetate for 503B.