The cleanest of the growth hormone secretagogues, by the pharmacology that got it into clinical development, and one that failed the only patient trials it was ever put through. What is sold under the name today is dosed for a purpose nobody has tested it for.
Summary
Ipamorelin is a synthetic pentapeptide, Aib-His-D-2-Nal-D-Phe-Lys-NH2, developed by Novo Nordisk in the 1990s. It stimulates growth hormone release through the ghrelin receptor with a potency similar to GHRP-6.1
Its distinguishing property is selectivity. In pigs it released growth hormone without raising ACTH or cortisol even at 200 times the effective dose, where GHRP-2 and GHRP-6 raised both.1
In healthy men an intravenous dose produced a single pulse of growth hormone peaking at 40 minutes, with a terminal half-life of about two hours.2
Two Phase 2 trials in patients, for recovery of bowel function after surgery, enrolled 117 and 320 people. The first found no significant difference from placebo. The second has never been published.34
In mice, ipamorelin increased body fat and food intake by a mechanism independent of growth hormone. That is the opposite of the effect it is sold for.5
No human study has measured body composition, muscle, fat, recovery or sleep on ipamorelin. Clinical development was discontinued.
The FDA lists ipamorelin acetate in Category 2 of its interim compounding policy for outsourcing facilities, citing immunogenicity and "serious adverse events including death" in the intravenous gastric motility study.6
Prohibited in sport under WADA section S2, which names it.7
The Most Common Error About This Compound
Reading selectivity as efficacy. Ipamorelin's claim to being the "cleanest" secretagogue is real and well documented: it raises growth hormone without raising cortisol or prolactin.1 That describes what it does not do. It says nothing about whether a growth hormone pulse two or three times a day does anything useful, which is the question every product page assumes and no study has asked.
Identity
What Is Ipamorelin?
Growth-hormone-releasing peptides, or GHRPs, are small synthetic peptides that act on the ghrelin receptor, GHS-R1a, to release growth hormone from the pituitary. They are a separate class from GHRH analogues such as CJC-1295 and tesamorelin, which act on a different receptor; the two classes are often combined for that reason.
Ipamorelin came out of a Novo Nordisk chemistry programme in the late 1990s that stripped the central dipeptide out of GHRP-1 and found a five-residue compound with two unnatural amino acids that kept the potency and lost the side effects. In rat pituitary cells and anaesthetised rats it matched GHRP-6; in conscious pigs it released growth hormone without touching FSH, LH, prolactin or TSH, and unlike the other GHRPs, without raising ACTH or cortisol.1 The company's code was NNC 26-0161.
What Does It Do in People?
Release growth hormone, once, for about an hour.
In a dose-escalation study, 40 healthy men received 15-minute intravenous infusions at five doses. Pharmacokinetics were dose-proportional with a terminal half-life of two hours. Growth hormone rose in a single episode, peaking at 0.67 hours and declining exponentially to negligible levels at every dose.2 A separate pharmacokinetic study in animals examined nasal absorption, which is why the compound was once considered for a nasal formulation.8
That pulse-and-fade profile is the basis for community protocols that inject it two or three times a day. The profile is real. Whether repeating it produces anything downstream has not been measured.
Evidence Base
What Did the Animal Studies Show?
Mixed, and the mix is instructive.
In adult female rats, three daily subcutaneous injections for 15 days increased the rate of long bone growth dose-dependently and increased body weight gain, without changing IGF-1 or bone turnover markers.9 A related study found ipamorelin and GHRP-6 increased bone mineral content in adult female rats.10 Those are the papers behind the bone and growth claims.
Then there is the 2001 mouse study, which compared twice-daily ipamorelin with growth hormone in growth-hormone-deficient and normal mice. Ipamorelin produced a small increase in body weight, increased fat pad weight relative to body weight in both groups, increased relative body fat on DEXA scanning, and raised serum leptin and food intake. Growth hormone decreased fat. The authors' conclusion: growth hormone secretagogues "increase body fat by GH-independent mechanisms that may include increased feeding."5
Ipamorelin is a ghrelin mimetic. Ghrelin is the hunger hormone. A compound sold for fat loss that increased fat and appetite in the one controlled comparison against growth hormone is not a paradox; it is the pharmacology working as described.
What Human Trials Exist?
Three, and none tested any use the compound is now sold for.
| Study | Population | Route and dose | Result |
|---|---|---|---|
| Gobburu 19992 | 40 healthy men | Single IV infusion, five doses | Growth hormone pulse; PK/PD model |
| NCT00672074, Beck 20143 | 117 adults after bowel resection | IV 0.03 mg/kg twice daily up to 7 days | Time to first tolerated meal 25.3 vs 32.6 hours, not significant (p = 0.15) |
| NCT012803444 | 320 adults after bowel resection | IV, Phase 2 | Completed May 2014; no results posted; not published |
The ileus programme belonged to Helsinn, which licensed the compound for its pro-motility effect on the gut, a ghrelin-receptor property demonstrated in rodents.11 The proof-of-concept trial was well tolerated, with treatment-emergent adverse events in 87.5 percent on drug and 94.8 percent on placebo, which is what a post-surgical population looks like, and it found no significant difference on any efficacy endpoint.3 The larger trial that followed it finished in 2014 and vanished. A 2026 review records that the negative result limited further clinical investigation.12
Is There Evidence for the Stack?
No. The combination of ipamorelin with CJC-1295 without DAC, typically 200 to 300 micrograms two or three times daily in eight-to-twelve-week cycles, is the most common way the compound is used. The 2026 review that catalogued those protocols describes the practice as "largely driven by anecdotal rationale," with controlled evidence for synergy or body-composition outcomes in healthy people remaining limited.12 "Limited" is generous. For the combination, it is absent; and the CJC-1295 half of it has never been studied in humans in the form used. The ONPEPS CJC-1295 entry covers that.
Safety
What Is Known?
In healthy men, a single intravenous dose was tolerated without notable events.2 In post-surgical patients receiving twice-daily intravenous doses for up to a week, adverse events were common in both arms and not obviously attributable to the drug.3 The 2026 review reports generally favourable tolerability and no long-term safety data.12
The FDA's position is more cautious and worth quoting. Its Category 2 entry states that ipamorelin acetate "contains unnatural amino acids, which add to the complexity of peptide characterization," that "a study published in literature identified serious adverse events including death when ipamorelin was administered intravenously for improving gastric motility," and that the agency "has not identified safety-related information regarding ipamorelin acetate via certain other injectable routes of administration," so it "lacks sufficient information to know whether the drug would cause harm if administered to humans via those routes."6
Two readings of that are both correct. Deaths in a trial of people recovering from bowel resection are not evidence the drug killed them, and the published abstract does not attribute any. And "certain other injectable routes" means subcutaneous, which is the only route anyone outside a hospital uses and the one for which the regulator says it has nothing.
What Is Unknown
Everything that would define a safety profile for the actual pattern of use: repeated subcutaneous dosing over months, in combination with a GHRH analogue, in women, in anyone over 60, or in anyone with a medical condition. The appetite and adiposity effect seen in mice has not been examined in humans. The theoretical concern attached to all growth hormone secretagogues, that sustained IGF-1 elevation might promote existing tumours, is unaddressed for this compound in any species over a relevant timeframe.
Sport and Drug Testing
Is Ipamorelin Prohibited?
Yes. WADA's Prohibited List names it under S2 among growth hormone secretagogues, prohibited at all times.7
Can It Be Detected?
Yes. Urinary metabolites after administration of ipamorelin and four other GHRPs have been characterised and a validated method published.13 Anti-doping laboratories have also characterised what is actually in black-market vials, which is not always the molecule on the label; the sourcing page covers that.14
Regulatory Status
Is It Approved Anywhere?
No. Novo Nordisk did not take it past early development, Helsinn's ileus programme ended without a filing, and no regulator has approved any product containing it.
Where Does It Stand on Compounding?
In a position slightly different from its stack partner. In September 2023 the FDA placed ipamorelin acetate in Category 2 of its interim policy for both 503A pharmacies and 503B outsourcing facilities. As of April 2026, the 503A nomination is listed as withdrawn by its nominator, but the substance remains in active Category 2 under the 503B policy, one of only a handful of peptides still there.6
Ipamorelin has not been before the Pharmacy Compounding Advisory Committee. It was not among the substances considered in December 2024, when the committee voted unanimously against CJC-1295, nor among the seven considered in July 2026.1516 It is not on the 503A bulks list, and no pharmacy in the United States has a lawful basis to compound it.
The practical consequence is that "CJC/Ipa" is a two-compound protocol in which one compound has been formally rejected for compounding and the other sits on the FDA's significant-safety-risk list. A clinic dispensing the pair is not operating in a gray area for either half.
Related ONPEPS Coverage
Ipamorelin sourcing and quality: unnatural amino acids, glycine analogues and the 503B list
Tesamorelin: the approved compound in the growth hormone pathway
FDA peptide news July 2026: the compounding advisory process explained
What Would Change This Page
A controlled human study of subcutaneous ipamorelin measuring body composition would be the first evidence for or against the use that drives every sale. Publication of the 320-patient ileus trial would complete the clinical record. Neither is registered or announced.
References
Raun K, Hansen BS, Johansen NL, Thøgersen H, Madsen K, Ankersen M, et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998;139(5):552-561. Open access. pubmed.ncbi.nlm.nih.gov/9849822
Gobburu JV, Agersø H, Jusko WJ, Ynddal L. Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharm Res. 1999;16(9):1412-1416. Paywalled. pubmed.ncbi.nlm.nih.gov/10496658
Beck DE, Sweeney WB, McCarter MD; Ipamorelin 201 Study Group. 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;29(12):1527-1534. Paywalled. pubmed.ncbi.nlm.nih.gov/25331030
ClinicalTrials.gov. NCT01280344. Safety and Efficacy of Ipamorelin Compared to Placebo for the Recovery of Gastrointestinal Function. Sponsor Helsinn Therapeutics (U.S.), Inc. Phase 2, 320 participants, completed May 2014, no results posted. Record retrieved 16 September 2026. clinicaltrials.gov/study/NCT01280344
Lall S, Tung LY, Ohlsson C, Jansson JO, Dickson SL. Growth hormone (GH)-independent stimulation of adiposity by GH secretagogues. Biochem Biophys Res Commun. 2001;280(1):132-138. Paywalled. pubmed.ncbi.nlm.nih.gov/11162489
US Food and Drug Administration. Category 2 of the Bulk Substances Nominated Under Sections 503A or 503B of the Federal Food, Drug, and Cosmetic Act. Entries for ipamorelin acetate. Content current as of 22 April 2026. fda.gov
World Anti-Doping Agency. The Prohibited List, section S2. Current edition. wada-ama.org
Johansen PB, Hansen KT, Andersen JV, Johansen NL. Pharmacokinetic evaluation of ipamorelin and other peptidyl growth hormone secretagogues with emphasis on nasal absorption. Xenobiotica. 1998;28(11):1083-1092. Paywalled. pubmed.ncbi.nlm.nih.gov/9879640
Johansen PB, Nowak J, Skjaerbaek C, Flyvbjerg A, Andreassen TT, Wilken M, et al. Ipamorelin, a new growth-hormone-releasing peptide, induces longitudinal bone growth in rats. Growth Horm IGF Res. 1999;9(2):106-113. Paywalled. pubmed.ncbi.nlm.nih.gov/10373343
Svensson J, Lall S, Dickson SL, Bengtsson BA, Rømer J, Ahnfelt-Rønne I, et al. The GH secretagogues ipamorelin and GH-releasing peptide-6 increase bone mineral content in adult female rats. J Endocrinol. 2000;165(3):569-577. Open access. pubmed.ncbi.nlm.nih.gov/10828840
Venkova K, Mann W, Nelson R, Greenwood-Van Meerveld B. Efficacy of ipamorelin, a novel ghrelin mimetic, in a rodent model of postoperative ileus. J Pharmacol Exp Ther. 2009;329(3):1110-1116. Open access. pubmed.ncbi.nlm.nih.gov/19289567
Dominikowski A, Rękoś Z, Olejarz M, Szczepanek-Parulska E, Domin R, Ruchała M. The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration. Front Endocrinol (Lausanne). 2026;17:1822475. Open access. pubmed.ncbi.nlm.nih.gov/42395176
Semenistaya E, Zvereva I, Thomas A, Thevis M, Krotov G, Rodchenkov G. Determination of growth hormone releasing peptides metabolites in human urine after nasal administration of GHRP-1, GHRP-2, GHRP-6, hexarelin, and ipamorelin. Drug Test Anal. 2015;7(10):919-925. Paywalled. pubmed.ncbi.nlm.nih.gov/25869809
Krug O, Thomas A, Malerød-Fjeld H, Dehnes Y, Laussmann T, Feldmann I, et al. Analysis of new growth promoting black market products. Growth Horm IGF Res. 2018;41:1-6. Paywalled. pubmed.ncbi.nlm.nih.gov/29864719
US Food and Drug Administration. Final Summary Minutes of the Pharmacy Compounding Advisory Committee Meeting, December 4, 2024. Approved 21 February 2025. fda.gov
US Food and Drug Administration. July 23-24, 2026: Meeting of the Pharmacy Compounding Advisory Committee. Docket FDA-2025-N-6895. fda.gov
Not Medical Advice
Ipamorelin is not approved for human use in any jurisdiction, no human dose has been established for any outcome other than a single growth hormone pulse, and it is prohibited in sport under WADA section S2. Consult a qualified healthcare provider before acting on anything here.
Evidence counts on the library index retrieved 23 July 2026. Literature and regulatory sources verified 16 September 2026. Re-verify before relying on any regulatory statement here.