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AMIRAVOResearch Library

Ipamorelin vs GHRP-2 (pralmorelin)

Ipamorelin and GHRP-2 are both synthetic growth hormone secretagogues that act at the ghrelin (GHS) receptor rather than the GHRH receptor 1,10. Ipamorelin is a pentapeptide developed at Novo Nordisk and described as the first GHS with GHRH-like selectivity, because in swine it raised growth hormone without raising ACTH or cortisol 1. GHRP-2, also called pralmorelin, is approved in Japan as a diagnostic agent for growth hormone secretion deficiency, where it has been marketed since February 2005 6. Neither is FDA-approved, and both appear on the FDA's compounding page of substances that may present significant safety risks, current as of 22 April 2026 5.

Unbranded reference vial illustrating Ipamorelin; not an actual product
Ipamorelin
Not approved — research use only
Unbranded reference vial illustrating GHRP-2; not an actual product
GHRP-2
Approved outside the US

Side by side

FieldIpamorelinGHRP-2
ClassSynthetic pentapeptide growth hormone secretagogue (ghrelin receptor agonist) 1Synthetic growth hormone-releasing peptide / ghrelin receptor agonist; generic name pralmorelin 6,7
Origin and structureAib-His-D-2-Nal-D-Phe-Lys-NH2, identified in a series lacking the central Ala-Trp dipeptide of GHRP-1; contains unnatural amino acids 1,2A hexapeptide derived from work on small GHRP analogues at Tulane University; marketed in Japan as pralmorelin hydrochloride 7,10
Proposed mechanismActs through a GHRP-like receptor; in rat pituitary cells its potency resembled GHRP-6, and in swine it did not raise ACTH or cortisol 1Stimulates growth hormone release at the GHS receptor; in conscious rats it raised growth hormone more than injected GHRH, and it also raised ACTH and corticosterone 10
Half-lifeAbout 2 hours terminal half-life in healthy subjects after intravenous administration, per FDA's review of a published study 2; about 27 minutes in rats 2Elimination half-life of about 0.42 to 0.69 hours in 18 healthy men after intravenous administration, per the Japanese package insert 6
Highest human trial phasePhase 2 (postoperative ileus after bowel resection, 117 patients) 3,4Approved diagnostic product in Japan; validation study in 77 healthy subjects and 58 patients with growth hormone deficiency 6,8
FDA statusNot FDA-approved; ipamorelin acetate is in 503B category 2 (added 29 September 2023) and also appears in the nominated-but-withdrawn section, as of 22 April 2026 5Not FDA-approved; GHRP-2 for injectable and nasal routes is in 503B category 2 (added 29 September 2023), as of 22 April 2026 5
Published human outcomesIn the phase 2 ileus trial, time to first tolerated meal did not differ significantly from placebo 3Peak growth hormone after GHRP-2 was much lower in patients with growth hormone deficiency than in healthy subjects, supporting its diagnostic use 8. In 7 healthy men, infusion was followed by greater food intake than saline 9
Safety signalsFDA notes two fatal serious adverse events in ipamorelin-treated participants in the ileus study, with causality unclear, plus higher rates of hypokalaemia and hyperglycaemia 2; the compounding page cites immunogenicity and characterisation concerns 5FDA is aware of reports of serious adverse events in patients who received GHRP-2, including increased insulin requirement, deaths of critically ill study subjects, infection and pancreatitis, with causality not established 5
WADA statusNamed under S2.2.4 as a growth hormone secretagogue; prohibited at all times (2026 List) 11Named under S2.2.4 as GHRP-2 (pralmorelin); prohibited at all times (2026 List) 11
Who funded the evidenceDiscovery work came from Novo Nordisk 1; the phase 2 ileus trial was sponsored by Helsinn Therapeutics (U.S.) and reported from Ochsner Clinic Foundation 3,4Preclinical characterisation came from Kaken Pharmaceutical, which holds the Japanese product 6,10; the food-intake study was supported by US NIH grants 9

Ipamorelin: what the data says

Ipamorelin was described in 1998 as the first GHS receptor agonist with selectivity for growth hormone release comparable to GHRH: in rat pituitary cells its potency resembled GHRP-6, and in swine it did not raise ACTH or cortisol while GHRP-6 and GHRP-2 did (cell and animal data) 1.

  • FDA's review reports linear pharmacokinetics with a terminal half-life of about 2 hours after intravenous administration in healthy subjects, and about 27 minutes in rats 2.
  • In a phase 2 randomized, double-blind trial of 117 patients after bowel resection (humans), median time to first tolerated meal was 25.3 hours with ipamorelin and 32.6 hours with placebo, a non-significant difference 3.
  • FDA states it found no pharmacokinetic or pharmacodynamic information for the subcutaneous route, and that published studies often do not specify which chemical form was used 2.

GHRP-2: what the data says

GHRP-2 is marketed in Japan as pralmorelin hydrochloride (GHRP Kaken 100 Injection) for the diagnosis of growth hormone secretion deficiency, with an approval number of 21600AMZ00573 and sales from February 2005 6.

  • In a validation study of 77 healthy subjects and 58 patients with growth hormone deficiency (humans), peak growth hormone was markedly lower in patients, and the authors proposed a diagnostic cut-off 8.
  • In rats and dogs (animal data), GHRP-2 raised growth hormone, and in conscious rats it also raised ACTH and corticosterone 10.
  • In 7 lean healthy men (humans), subcutaneous infusion was followed by about 36% greater intake at a buffet meal than saline, alongside a rise in serum growth hormone 9.
  • A 2004 drug profile notes that development rights passed through several companies and that the Japanese diagnostic indication was the lead use 7.

Key research differences

  • Hormone selectivity: in swine, ipamorelin raised growth hormone without raising ACTH or cortisol, whereas GHRP-2 raised both 1.
  • Approval: GHRP-2 is an approved diagnostic product in Japan 6; ipamorelin has no approval identified in the sources reviewed 2,5.
  • Human endpoints studied: ipamorelin's largest trial was a therapeutic study in postoperative ileus that missed its endpoint 3, while GHRP-2's human data centre on diagnostic testing and appetite 8,9.
  • Half-life: about 2 hours for intravenous ipamorelin in healthy subjects 2 versus about 0.42 to 0.69 hours for intravenous pralmorelin in healthy men 6, from different sources and assays.
  • FDA listing: both are 503B category 2 as of 22 April 2026, but the GHRP-2 entry is limited to injectable and nasal routes 5.

Where the evidence is limited

No head-to-head human trial was located. The only direct comparisons are animal and cell experiments in which ipamorelin and GHRP-2 were tested side by side for hormone release 1. Their human evidence serves different purposes: a failed therapeutic trial for ipamorelin and diagnostic validation for GHRP-2 3,8. FDA reviewers note that published ipamorelin studies often do not state which chemical form was used, limiting what can be concluded about marketed material 2. Pharmacokinetic values come from different routes, populations and sources 2,6.

Frequently asked questions

Is GHRP-2 approved anywhere?
Yes, in Japan: pralmorelin hydrochloride is approved as a diagnostic agent for growth hormone secretion deficiency and has been marketed since February 2005 6. It is not FDA-approved 5.
Is ipamorelin more selective than GHRP-2?
In swine, ipamorelin raised growth hormone without raising ACTH or cortisol, while GHRP-2 and GHRP-6 raised both; this is animal data and was reported by the group that developed ipamorelin 1.
Have ipamorelin and GHRP-2 been compared in people?
No head-to-head human trial was located. Side-by-side comparisons exist only in cell and animal experiments 1.
What safety concerns has the FDA raised?
For ipamorelin, FDA cites two fatal serious adverse events among treated participants in a postoperative ileus study, with causality unclear 2. For GHRP-2, it cites reports of serious adverse events including increased insulin requirement, deaths in critically ill study subjects, infection and pancreatitis, with causality not established 5.

References

  1. Ipamorelin, the first selective growth hormone secretagogue European Journal of Endocrinology. 1998
  2. FDA Briefing Document, Pharmacy Compounding Advisory Committee, 29 October 2024: Ipamorelin-related bulk drug substances FDA. 2024
  3. 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
  4. Safety and Efficacy of Ipamorelin for Management of Post-Operative Ileus (NCT00672074) ClinicalTrials.gov. 2014
  5. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks (content current as of 04/22/2026) FDA (Human Drug Compounding). 2026
  6. Package insert: GHRP Kaken 100 Injection (pralmorelin hydrochloride), 3rd revision July 2025 PMDA (Japan). 2025
  7. Pralmorelin: GHRP 2, GPA 748, growth hormone-releasing peptide 2, KP-102 Drugs in R&D. 2004
  8. A simple diagnostic test using GH-releasing peptide-2 in adult GH deficiency European Journal of Endocrinology. 2007
  9. Growth hormone releasing peptide-2 (GHRP-2), like ghrelin, increases food intake in healthy men Journal of Clinical Endocrinology and Metabolism. 2005
  10. Pharmacological characteristics of KP-102 (GHRP-2), a potent growth hormone-releasing peptide Arzneimittel-Forschung. 2004
  11. Prohibited List 2026 (in force 1 January 2026) World Anti-Doping Agency. 2026

For research use only. Not for human or veterinary use. Not a drug, food, or dietary supplement. This page compares published research and is not medical advice or a recommendation.