Ipamorelin is usually sold in a pair with CJC-1295 as a "GH stack." It is the better-studied half, which is not saying much: a pharmacokinetic study in volunteers and one randomised trial that failed. It is also the one peptide on this site that FDA has kept in Category 2 rather than moving to the withdrawn list.
What it is
Ipamorelin is a synthetic pentapeptide developed by Novo Nordisk in the 1990s (PubMed 9849822). It is a growth hormone secretagogue: it binds the ghrelin receptor and provokes the pituitary to release a pulse of growth hormone. Its selling point in the original paper was selectivity: unlike the earlier GHRP-2 and GHRP-6, it did not raise cortisol or prolactin at GH-releasing doses in the animal work.
Novo did not take it forward. A later company, Helsinn, ran a phase 2 trial in a surgical indication, which is the only efficacy trial that exists.
The human evidence
| Year | Design | Result | PubMed |
|---|---|---|---|
| 1999 | Randomised, placebo-controlled pharmacokinetic and GH-response study in healthy volunteers, intravenous | Dose-proportional kinetics; terminal half-life about 2 hours; each dose produced one GH pulse peaking at 0.67 hours then declining to negligible levels. | 10496658 |
| 2014 | Multicentre, randomised, double-blind, placebo-controlled phase 2; 117 adults after bowel resection; intravenous twice daily for up to 7 days | Median time to first tolerated solid meal 25.3 h vs 32.6 h, p = 0.15. Any treatment-emergent adverse event: 87.5% ipamorelin vs 94.8% placebo, in a post-surgical population where almost everyone has events. | 25331030 |
The phase 2 study is the only randomised outcome trial of ipamorelin in humans. It was well designed for its question and it did not reach significance. Nothing has been published since. There is no human trial of subcutaneous ipamorelin for body composition, sleep, bone, recovery or ageing, which are the uses it is sold for.
Regulatory status
FDA placed ipamorelin acetate in Category 2 under the 503B interim policy on September 29, 2023, and it remains listed there on the Category 2 page (content current as of April 22, 2026). FDA's stated concerns: risk of immunogenicity for certain routes from aggregation or peptide-related impurities; unnatural amino acids that add to the complexity of characterisation; and a study in the literature that "identified serious adverse events including death when ipamorelin was administered intravenously for improving gastric motility."
The Pharmacy Compounding Advisory Committee discussed ipamorelin on October 29, 2024. FDA's briefing materials recommended against adding it to the 503A bulks list. It is not on the list, not in Category 1, and not an ingredient of any approved drug. The compounding site's page on PCAC and the bulks lists covers the meeting.
Safety signals
FDA's citation of serious adverse events including death refers to a published study of intravenous ipamorelin for gastric motility. The phase 2 population was adults recovering from bowel resection, in whom serious events occur in both arms, and the paper's own conclusion was that the drug was well tolerated. FDA's point is narrower: the human safety data are from one intravenous trial in sick patients, and there are none for the subcutaneous use the compounded product is sold for. Immunogenicity of a peptide with non-natural residues has not been measured in humans.
Grade: C + X
C because one randomised controlled trial exists. A negative RCT still counts as an RCT on this scale; the grade describes the kind of evidence, not whether it favours the product. The trial result is in the table. X because FDA's safety concern is current and specific. The methodology page explains why a failed trial and a successful one can share a letter, and why the page, not the letter, is what you should read.
Questions people ask
Has ipamorelin been shown to work in a human trial?
No. The one randomised, placebo-controlled efficacy trial (PubMed 25331030) tested intravenous ipamorelin after bowel surgery in 117 patients. Median time to a first tolerated meal was 25.3 hours with ipamorelin and 32.6 hours with placebo, p = 0.15, which is not statistically significant. No trial has tested it for body composition, sleep, recovery or ageing.
Why is ipamorelin still in Category 2 when other peptides were withdrawn?
FDA's Category 2 page (content current as of April 22, 2026) lists ipamorelin acetate under the 503B interim policy as of September 29, 2023 and also on the 503A withdrawn list. FDA's stated reasons: immunogenicity risk from aggregation or impurities, unnatural amino acids that complicate characterisation, and a published study reporting serious adverse events including death when ipamorelin was given intravenously for gastric motility.
Is ipamorelin a form of growth hormone?
No. It is a pentapeptide that acts on the ghrelin receptor (GHS-R1a) to trigger a pulse of the body's own growth hormone. In the 1999 volunteer study each dose produced a single GH pulse peaking at about 40 minutes and falling back to negligible levels; the terminal half-life was about 2 hours.
Sources
- FDA: Certain Bulk Drug Substances for Use in Compounding That May Present Significant Safety Risks (content current as of April 22, 2026) Accessed September 4, 2026.
- FDA: Pharmacy Compounding Advisory Committee (October 29, 2024 meeting materials via committee page) Accessed September 4, 2026.
- Gobburu JV et al. Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharm Res 1999. PubMed 10496658 Accessed September 4, 2026.
- Beck DE et al. Prospective, randomized, controlled, proof-of-concept study of the ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients. Int J Colorectal Dis 2014. PubMed 25331030 Accessed September 4, 2026.
- Raun K et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol 1998. PubMed 9849822 Accessed September 4, 2026.
Canonical URL: https://formblendspeptides.com/peptides/ipamorelin. Written by the FormBlends editorial team. This page is educational and is not medical advice; see the medical disclaimer.