# Ipamorelin - Canonical: https://residue.info/c/ipamorelin/ - Also called: NNC 26-0161, Ipamorelin acetate - Evidence grade: C (Limited / early human data). One small randomized proof-of-concept trial (postoperative ileus) showed no significant benefit; the rest of the record is animal and pharmacology work. - Status: Not FDA-approved · FDA compounding Category 2 (503B) - PubChem CID: 9831659 - Updated: 2026-10-19 · Reviewed by: Residue Editorial Team Ipamorelin is a synthetic pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH2) that stimulates growth hormone release through the ghrelin (GH-secretagogue) receptor without raising other pituitary hormones in animal studies [1]. Its only published randomized human efficacy trial, in 114 bowel-surgery patients, found no significant benefit over placebo [2]. It is not FDA-approved, and FDA lists ipamorelin acetate in compounding Category 2 for outsourcing facilities [3]. ## Key findings - Ipamorelin released GH with potency and efficacy similar to GHRP-6 in rat pituitary cells, anesthetized rats and swine [1]. (anchor: https://residue.info/c/ipamorelin/#kf-pmid-9849822) - In swine, it did not change FSH, LH, prolactin or TSH — the basis for calling it the first selective GH secretagogue [1]. (anchor: https://residue.info/c/ipamorelin/#kf-pmid-9849822-2) - A randomized proof-of-concept trial in 114 bowel-resection patients found median time to first tolerated meal of 25.3 versus 32.6 hours (p=0.15), with no significant differences on any efficacy analysis [2]. (anchor: https://residue.info/c/ipamorelin/#kf-pmid-25331030) - In rats, repeated intravenous dosing improved postoperative gut transit and food intake [4], and subcutaneous dosing increased longitudinal bone growth [5]. (anchor: https://residue.info/c/ipamorelin/#kf-pmid-19289567) - FDA placed ipamorelin acetate in Category 2 for 503B outsourcing facilities on September 29, 2023, citing immunogenicity risk and a reported death with intravenous use [3]. (anchor: https://residue.info/c/ipamorelin/#kf-fda-cat2) ## Effects by system - GH release (grade D): Dose-dependent GH release via a GHRP-like receptor in animal models [1]. (anchor: https://residue.info/c/ipamorelin/#effect-gh-release) - Gastrointestinal motility (grade C): Improved transit in a rat ileus model [4]; no significant effect in the human proof-of-concept trial [2]. (anchor: https://residue.info/c/ipamorelin/#effect-gastrointestinal-motility) - Bone growth (grade D): Longitudinal bone growth rose from 42 to 52 µm/day in adult female rats [5]. (anchor: https://residue.info/c/ipamorelin/#effect-bone-growth) - Safety signal (grade C): FDA cites a published report of serious adverse events including death with intravenous administration for gastric motility [3]. (anchor: https://residue.info/c/ipamorelin/#effect-safety-signal) ## How does Ipamorelin work? Ipamorelin came out of a chemistry program building on growth-hormone-releasing peptide-1 (GHRP-1): it is a pentapeptide, Aib-His-D-2-Nal-D-Phe-Lys-NH2, lacking GHRP-1's central Ala-Trp dipeptide. Profiling with GHRP and GHRH antagonists showed it acts like GHRP-6, via a GHRP-like receptor — the receptor later identified as the ghrelin receptor [1][4]. Two of its five residues are non-standard (Aib and D-2-naphthylalanine), which is why PubChem's one-letter sequence (Figure 1) shows them as X. What set it apart in 1998 was selectivity. In conscious swine, ipamorelin released GH with an ED50 of 2.3 nmol/kg without affecting FSH, LH, prolactin or TSH, leading the authors to call it the first selective GH secretagogue [1]. ## What have studies found? **Animal pharmacology.** In rat pituitary cells and anesthetized rats, ipamorelin's potency and efficacy were comparable to GHRP-6 [1]. Given subcutaneously three times daily for 15 days to adult female rats, it dose-dependently increased longitudinal bone growth (from 42 to 44, 50 and 52 µm/day) and body-weight gain without changing total IGF-1 [5]. In a rat model of postoperative ileus, repeated intravenous doses increased fecal output, food intake and weight gain [4]. **The human trial.** That rodent work led to a randomized, placebo-controlled proof-of-concept study in bowel-resection patients. Of 117 enrolled, 114 were analyzed. Median time to first tolerated meal was 25.3 hours with ipamorelin versus 32.6 hours with placebo (p=0.15), and there were no significant differences in key or secondary efficacy analyses. The regimen — 0.03 mg/kg twice daily for up to seven days — was well tolerated. The authors noted the study was small and enrolled patients with diverse conditions [2]. **What is missing.** We found no published controlled human trial of ipamorelin for the uses it is most often searched for, such as body composition, sleep or aging. PubMed tags only two records as clinical trials [6]. FDA's Category 2 entry for ipamorelin acetate applies to 503B outsourcing facilities and was added on September 29, 2023. The agency cites potential immunogenicity from aggregation or impurities, notes that unnatural amino acids complicate characterization, and refers to a published study reporting serious adverse events including death when ipamorelin was given intravenously for gastric motility [3]. It also appears on FDA's list of substances whose compounding nominations were withdrawn [3]. ## What is still unknown? - **Any controlled human efficacy data** outside postoperative ileus. - **Safety by route.** FDA states it has not identified safety-related information for certain other injectable routes [3]. ## Frequently asked questions **Is ipamorelin FDA-approved?** No. Drugs@FDA returned no application. FDA lists ipamorelin acetate in Category 2 — bulk substances that may present significant safety risks — for 503B outsourcing facilities, effective September 29, 2023 [3]. **How does ipamorelin work?** It stimulates GH release through a GHRP-like (ghrelin) receptor rather than the GHRH receptor; GHRP and GHRH antagonist profiling confirmed the pathway in the original pharmacology paper [1]. **Has ipamorelin been tested in humans?** Yes, in a small way. A randomized trial in 114 bowel-resection patients tested 0.03 mg/kg intravenously twice daily for up to 7 days for postoperative ileus; it was well tolerated but showed no significant efficacy [2]. ClinicalTrials.gov lists only a handful of studies [7]. **What are the side effects of ipamorelin?** In the ileus trial, treatment-emergent adverse events occurred in 87.5% on ipamorelin and 94.8% on placebo, reflecting the post-surgical setting [2]. FDA's Category 2 entry cites a literature report of serious adverse events including death with intravenous use [3]. **What is the difference between ipamorelin and sermorelin?** Sermorelin acts on the GHRH receptor [8]; ipamorelin acts on the ghrelin/GH-secretagogue receptor [1]. Sermorelin was once an approved product; ipamorelin never was. ## Sources [1] Ipamorelin, the first selective growth hormone secretagogue. Raun K et al. Eur J Endocrinol. 1998. https://pubmed.ncbi.nlm.nih.gov/9849822/ [2] Prospective, randomized, controlled, proof-of-concept study of the Ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients. Beck DE et al. Int J Colorectal Dis. 2014. https://pubmed.ncbi.nlm.nih.gov/25331030/ [3] Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks. U.S. FDA, content current as of 04/22/2026. https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks [4] Efficacy of ipamorelin, a novel ghrelin mimetic, in a rodent model of postoperative ileus. Venkova K et al. J Pharmacol Exp Ther. 2009. https://pubmed.ncbi.nlm.nih.gov/19289567/ [5] Ipamorelin, a new growth-hormone-releasing peptide, induces longitudinal bone growth in rats. Johansen PB et al. Growth Horm IGF Res. 1999. https://pubmed.ncbi.nlm.nih.gov/10373343/ [6] PubMed search: (ipamorelin[tiab]). 51 records at fetch. https://pubmed.ncbi.nlm.nih.gov/?term=(ipamorelin%5Btiab%5D) [7] ClinicalTrials.gov registry search: ipamorelin. 3 registered studies at fetch. https://clinicaltrials.gov/search?intr=ipamorelin [8] Sermorelin: a review of its use in the diagnosis and treatment of children with idiopathic growth hormone deficiency. Prakash A & Goa KL BioDrugs. 1999. https://pubmed.ncbi.nlm.nih.gov/18031173/ --- From Residue. Research and education only; not medical advice. Quote with attribution and a link to the canonical page.