Ipamorelin Canada: Selective GH Secretagogue Research Guide
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Ipamorelin: Selectivity, Evidence and Regulatory Status in Canada
By the ThePeptide.ca Research Team · Written from primary literature · Research use only · Last updated 3 August 2026
Ipamorelin is a synthetic pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH₂) that acts as a selective growth hormone secretagogue at the GHS receptor — the same receptor ghrelin binds. Its defining property, established in 1998, is selectivity: it stimulates growth hormone release without the increases in ACTH and cortisol produced by earlier GHRPs, even at doses 200-fold above its effective dose. Its one controlled human efficacy trial, in postoperative ileus, did not meet its primary endpoint. It is not approved by Health Canada or the FDA and holds no DIN.
Key takeaways
- It is a pentapeptide GHS-R agonist, not a GHRH analogue — a mechanistic distinction that matters when comparing it to CJC-1295 or sermorelin.
- Selectivity is the whole point. GHRP-6 and GHRP-2 raise ACTH and cortisol substantially; Ipamorelin does not, even at 200× its GH ED₅₀.
- Potency is well characterised: EC₅₀ of 1.3 ± 0.4 nmol/l in vitro and ED₅₀ of 2.3 ± 0.03 nmol/kg in swine.
- The human efficacy evidence is negative. A 117-patient placebo-controlled trial found no statistically significant benefit (p = 0.15 on the primary endpoint).
- It was well tolerated in that trial — adverse events were lower than placebo (87.5% vs 94.8%). Safety and efficacy are separate findings.
- Regulatory position is unsettled. No Health Canada DIN; placed in FDA 503A Category 2 in 2023 and currently the subject of litigation.
What Ipamorelin is
Ipamorelin is a synthetic pentapeptide — five amino acids — with the sequence Aib-His-D-2-Nal-D-Phe-Lys-NH₂. It was developed in the 1990s at Novo Nordisk and first characterised in a 1998 paper in the European Journal of Endocrinology whose title states the claim directly: Ipamorelin, the first selective growth hormone secretagogue.
| Class | Growth hormone secretagogue (GHS); ghrelin receptor agonist |
|---|---|
| Sequence | Aib-His-D-2-Nal-D-Phe-Lys-NH₂ |
| Length | Pentapeptide (5 residues) |
| Receptor | GHS-R (the GHRP receptor) — not the GHRH receptor |
| In-vitro potency | EC₅₀ 1.3 ± 0.4 nmol/l |
| In-vivo potency | ED₅₀ 2.3 ± 0.03 nmol/kg (swine) |
| Regulatory status | No Health Canada DIN; not FDA approved |
How it works
Ipamorelin binds the growth hormone secretagogue receptor (GHS-R), the receptor that the hormone ghrelin acts on. Activating it triggers release of growth hormone already stored in the somatotroph cells of the anterior pituitary. It does not create growth hormone; it prompts release of what is there.
The 1998 work confirmed the receptor mechanism pharmacologically rather than by assumption: the GH response to Ipamorelin was blocked by a GHRP-receptor antagonist but not by a GHRH antagonist. That is the experiment that establishes it as a GHRP-like agonist and separates it from the GHRH analogue class entirely.
The selectivity finding that made it notable
Earlier growth hormone releasing peptides worked, but they were messy. GHRP-6 and GHRP-2 release growth hormone and also drive substantial release of ACTH and cortisol — a stress-axis response that confounds interpretation of any GH result. GHRP-6 additionally produces marked appetite stimulation through the same ghrelin pathway.
Ipamorelin was the compound that separated those effects. In the 1998 characterisation, GHRP-6 and GHRP-2 “induced large and significant increases in plasma ACTH and cortisol levels” while Ipamorelin produced minimal effect on either — even at doses 200-fold higher than its GH ED₅₀ — a profile matching GHRH rather than the other GHRPs.
This is the single reason Ipamorelin remains a reference compound in GH-axis research nearly three decades later. It is a tool for asking what growth hormone does without simultaneously activating the HPA axis.
↑ Back to topWhat the one controlled human trial actually found
Ipamorelin has been tested in a randomised, double-blind, placebo-controlled human trial — and it did not meet its primary endpoint. This is the part of the Ipamorelin story that is almost universally omitted, and it is the most useful thing on this page.
The trial (Beck et al., International Journal of Colorectal Disease, 2014) was a multicentre Phase 2 proof-of-concept study in 117 patients undergoing open or laparoscopic small and large bowel resection, testing whether Ipamorelin would speed recovery from postoperative ileus — the temporary gut shutdown that follows abdominal surgery.
| Trial parameter | Detail |
|---|---|
| Design | Multicentre, double-blind, placebo-controlled Phase 2 |
| Patients | 117 enrolled; 114 in safety and modified intent-to-treat analyses |
| Study period | From postoperative day 1 to day 7 or discharge |
| Primary endpoint | Time to tolerating a standardised solid meal |
| Result | Median 25.3 h (Ipamorelin) vs 32.6 h (placebo) — p = 0.15, not significant |
| Adverse events | 87.5% (Ipamorelin) vs 94.8% (placebo) |
The numerical difference favoured Ipamorelin by about seven hours, but at p = 0.15 that result is well short of statistical significance — it is consistent with chance. The authors reported “no significant differences between ipamorelin and placebo in the key and secondary efficacy analyses.”
Everything else in the Ipamorelin literature — the GH release data, the selectivity profile, bone and body-composition work — is preclinical, largely in rodents and swine. Any page presenting Ipamorelin as clinically proven in humans is not describing the published record.
↑ Back to topIpamorelin compared with other GHRPs
| Compound | GH release | ACTH / cortisol | Appetite effect |
|---|---|---|---|
| Ipamorelin | Yes | Minimal, even at 200× ED₅₀ | Minimal |
| GHRP-2 | Yes, potent | Large, significant increases | Moderate |
| GHRP-6 | Yes | Large, significant increases | Marked |
| Hexarelin | Yes, potent | Substantial; tachyphylaxis reported | Modest |
Ipamorelin vs CJC-1295 — different receptors, not competing options
These two are constantly framed as alternatives. They are not; they act on different receptors, which is precisely why they are studied as a pair.
| Ipamorelin | CJC-1295 | |
|---|---|---|
| Class | GHS / ghrelin mimetic | GHRH analogue |
| Receptor | GHS-R | GHRH receptor |
| Primary action | Initiates GH release | Increases pulse amplitude |
| Effect on cortisol | Minimal | Not a primary mechanism |
| Length | 5 residues | 29-residue analogue (DAC variant extends half-life) |
Our comparison of the two, including the DAC and no-DAC distinction, is in the CJC-1295 + Ipamorelin guide.
↑ Back to topRegulatory status
In Canada, Ipamorelin has no Drug Identification Number and is not authorised by Health Canada as a therapeutic product. It may not be sold or marketed for human use. Our full account of the Canadian framework — including why “research use only” labelling is not a legal exemption — is in Are peptides legal in Canada?
In the United States the position is contested and actively moving. In September 2023 the FDA placed more than a dozen peptides, Ipamorelin acetate among them, into Category 2 of the interim 503A bulk drug substances list — a designation that effectively bars their use in pharmacy compounding. Ipamorelin acetate is one of four peptides named in Evexias and Farmakeio v. FDA, litigation challenging that placement.
Notably, Ipamorelin was not among the seven peptides reviewed at the Pharmacy Compounding Advisory Committee meeting of 23–24 July 2026 (BPC-157, KPV, TB-500, MOTS-C, Emideltide, Semax and Epitalon). A second PCAC meeting covering five further peptides is expected before the end of February 2027. Even a favourable recommendation would require notice-and-comment rulemaking, which typically takes more than a year.
Handling and verification
Ipamorelin is supplied as a lyophilised powder. Like other small peptides it is sensitive to heat, moisture and repeated freeze–thaw cycling; our storage and stability guide covers handling in detail.
Because Ipamorelin is short, comparatively inexpensive to synthesise, and sold widely, it is a compound where independent verification matters. A certificate of analysis should state the lot number, the assay method and wavelength, the measured result, and the testing laboratory — and identity should be confirmed by mass spectrometry, not inferred from a purity percentage. Our guide on reading a peptide COA sets out the checks, and our published lot certificates are linked to the testing laboratory’s own records.
↑ Back to topFrequently asked questions
What is Ipamorelin?
Ipamorelin is a synthetic pentapeptide with the sequence Aib-His-D-2-Nal-D-Phe-Lys-NH₂ that acts as an agonist at the growth hormone secretagogue receptor, the receptor ghrelin binds. It stimulates release of growth hormone stored in the anterior pituitary. It was developed at Novo Nordisk and first characterised in 1998.
How is Ipamorelin different from CJC-1295?
They act on different receptors. Ipamorelin is a growth hormone secretagogue acting at GHS-R and can initiate GH release. CJC-1295 is a GHRH analogue acting at the GHRH receptor and principally increases the amplitude of existing GH pulses. In the 1998 characterisation, Ipamorelin's effect was blocked by a GHRP-receptor antagonist but not by a GHRH antagonist, confirming the mechanistic separation.
Why is Ipamorelin described as selective?
Because it releases growth hormone without meaningfully raising ACTH and cortisol. Earlier growth hormone releasing peptides, GHRP-6 and GHRP-2, produced large and significant increases in both. Ipamorelin showed minimal effect even at doses 200-fold above its GH ED₅₀, giving it a selectivity profile comparable to GHRH.
Has Ipamorelin been tested in humans?
Yes, once in a substantial controlled trial. A multicentre, double-blind, placebo-controlled Phase 2 study in 117 bowel-resection patients tested it for postoperative ileus. Median time to tolerating a solid meal was 25.3 hours with Ipamorelin versus 32.6 hours with placebo, but at p = 0.15 the difference was not statistically significant, and the authors reported no significant differences in the key or secondary efficacy analyses.
Was Ipamorelin found to be unsafe in that trial?
No. Adverse events occurred in 87.5% of the Ipamorelin arm and 94.8% of the placebo arm, and the authors described it as well tolerated. The trial failed on efficacy, not on safety. Those are separate findings and should not be conflated.
Is Ipamorelin legal in Canada?
Ipamorelin has no Health Canada Drug Identification Number and is not authorised as a therapeutic product, so it cannot be sold or marketed for human use in Canada. It is supplied as a research-use-only laboratory material. Health Canada has stated that research-use-only labelling does not by itself make a product legal or exempt from regulatory requirements.
Why was Ipamorelin placed in FDA Category 2?
In September 2023 the FDA moved more than a dozen peptides, including ipamorelin acetate, into Category 2 of the interim 503A bulk drug substances list, a designation that effectively prohibits their use in pharmacy compounding. That placement is being challenged in litigation, Evexias and Farmakeio v. FDA, in which ipamorelin acetate is one of four named peptides.
Does Ipamorelin increase appetite?
Minimally, in contrast to GHRP-6. Although Ipamorelin acts on the same ghrelin receptor pathway that mediates appetite signalling, the 1998 characterisation found it did not produce the marked appetite stimulation associated with GHRP-6.
What is Ipamorelin's molecular potency?
Its in-vitro EC₅₀ for growth hormone release was reported as 1.3 ± 0.4 nmol/l, and its in-vivo ED₅₀ in swine as 2.3 ± 0.03 nmol/kg.
Related research resources
- CJC-1295 + Ipamorelin research guide — the two mechanisms compared
- Are peptides legal in Canada? — the regulatory framework from primary sources
- How to read a peptide COA · Our published lot certificates
- Peptides ranked by evidence — where Ipamorelin sits relative to others
- Storage and stability guide
Sources
- Raun K, Hansen BS, Johansen NL, et al. Ipamorelin, the first selective growth hormone secretagogue. European Journal of Endocrinology. 1998;139(5):552–561. PMID 9849822.
- Beck DE, Sweeney WB, McCarter MD, et al. Prospective, randomized, controlled, proof-of-concept study of the ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients. International Journal of Colorectal Disease. 2014;29(12). link.springer.com.
- U.S. Food and Drug Administration. Bulk Drug Substances Used in Compounding Under Section 503A of the FD&C Act. fda.gov.
- Hyman, Phelps & McNamara. FDA’s Pep(tide) Rally: What Compounders and Industry Need to Know. April 2026. thefdalawblog.com.
- Buscail E, et al. Postoperative ileus: a pharmacological perspective. British Journal of Pharmacology. 2022. bpspubs.onlinelibrary.wiley.com.
Changelog. 3 August 2026 — First published. Written from the 1998 primary characterisation (sequence, EC₅₀/ED₅₀, the 200-fold selectivity finding and the receptor-antagonist experiment) and the 2014 controlled human trial, including its negative primary endpoint at p = 0.15. Regulatory position current as of the July 2026 PCAC meeting.