# Buy Ipamorelin — Selective GHS-R1a Research Literature

> Ipamorelin (NNC 26-0161) is a pentapeptide ghrelin receptor agonist studied for pulsatile GH release, bone formation, GI motility, and nitrogen balance. Research summary with 18 citations. For research purposes only.

## What Ipamorelin Is

Ipamorelin (IUPAC designation: Aib-His-D-2-Nal-D-Phe-Lys-NH2; CAS 170851-70-4; molecular weight 711.86 Da; molecular formula C38H49N9O5) is a synthetic pentapeptide that acts as a selective agonist at the growth hormone secretagogue receptor type 1a (GHS-R1a), also known as the ghrelin receptor. It was developed at Novo Nordisk Pharma A/S under the research code NNC 26-0161 and first characterized pharmacologically by Raun et al. in 1998. [1]

The compound was derived from GHRP-1 by removing the central Ala-Trp dipeptide and substituting alpha-aminoisobutyric acid (Aib) at the N-terminus. The Aib modification confers metabolic stability against peptidase cleavage — a design feature confirmed by pharmacokinetic data showing that 60–80% of an administered dose is recovered from bile and urine as intact peptide, with plasma clearance approximately five-fold lower than GHRP-6. [11]

GHS-R1a is expressed on anterior pituitary somatotrophs, hypothalamic appetite-regulatory neurons, and enteric nervous system cells. When ipamorelin binds the pituitary somatotroph GHS-R1a, it triggers intracellular calcium mobilization via Gq/11-protein-coupled signaling, which drives a discrete pulse of growth hormone (GH) release. That GH pulse peaks at approximately 40 minutes post-administration and decays to negligible levels within 2–3 hours, consistent with the compound's terminal half-life of approximately 2 hours in human volunteers. [12]

What distinguishes ipamorelin from earlier GHRP-class compounds is selectivity. GHRP-2 and GHRP-6 both stimulate ACTH/cortisol and prolactin secretion at doses near their GH-releasing thresholds. Ipamorelin does not meaningfully elevate ACTH or cortisol even at doses 200-fold above its GH-releasing ED50 in rats. [1] A 2020 review of GHS pharmacology designated ipamorelin the "prototypical selective GHS." [17]

## What the Research Record Shows

Eighteen peer-reviewed citations index this site's research record. The literature spans bone biology, GI motility, body composition, nitrogen balance, pharmacokinetics, and oncology-adjacent cachexia models. The majority of data comes from rodent in vivo studies (primarily rat); one Phase 2 randomized controlled trial in humans was conducted (Beck et al., 2014; NCT00672074; N=114) targeting postoperative ileus after bowel resection. [10]

**Bone and body composition.** Subcutaneous ipamorelin at 18–450 mcg/day (divided doses) for 15 days increased longitudinal bone growth rate from 42 to 52 mcm/day in adult female rats in a dose-dependent manner. [2] Continuous subcutaneous infusion at 0.5 mg/kg/day for 12 weeks significantly increased tibial and vertebral bone mineral content via periosteal expansion. [4] In glucocorticoid-treated rats, 100 mcg/kg three times daily for three months produced a four-fold increase in periosteal bone formation rate and significant recovery of muscle tetanic tension. [3]

**GI motility and postoperative ileus.** A single intravenous dose (1 mg/kg) reduced time to first bowel movement in a rodent postoperative ileus model. [8] Intravenous ipamorelin at 0.014 mcmol/kg reduced gastric radioactivity retention from 78% to approximately 52%, approaching non-operated control levels of 44%. [9] The 2014 Phase 2 human trial found the compound well tolerated, with a 7.3-hour numeric reduction in time to first tolerated meal that did not reach statistical significance (p=0.15). [10]

**Nitrogen balance.** Ipamorelin at 0.5 mg/kg/day counteracted glucocorticoid-induced nitrogen wasting in prednisolone-treated rats, reducing hepatic urea-nitrogen synthesis capacity by 20%. [7]

**Recent data (2024–2025).** Intraperitoneal ipamorelin inhibited cisplatin-induced weight loss by approximately 24% during the delayed phase (48–72 h post-cisplatin) in a ferret model via peripheral mechanism. [15]

## Regulatory and Anti-Doping Status

Ipamorelin has no FDA-approved indication for any human therapeutic use. Ipamorelin acetate and free base were nominated for the FDA 503A compounding bulk drug substance list (docket FDA-2024-N-4188); the nomination was withdrawn by the nominator in September 2024. [16]

Ipamorelin is classified as a prohibited substance under the WADA Prohibited List S2 — Peptide Hormones, Growth Factors, Related Substances and Mimetics, subcategory S2.2.4 Growth Hormone Secretagogues. The prohibition applies both in-competition and out-of-competition. No Therapeutic Use Exemption is available for competitive athletes. [18]

## Reagent-Grade Sourcing Standards

Research-grade ipamorelin is characterized by purity of ≥98% by reversed-phase HPLC, with molecular weight confirmed by LC-MS at 711.86 Da. Standard Certificate of Analysis documentation includes lot number, HPLC purity percentage, amino acid analysis, mass spectrometry identity confirmation, and storage specifications. Lyophilized powder is stable long-term at −20°C. [16]

## References

[1] Raun K, Hansen BS, Johansen NL, Thogersen H, Madsen K, Ankersen M, Andersen PH. Ipamorelin, the first selective growth hormone secretagogue. European Journal of Endocrinology. 1998;139(5):552-561. DOI:10.1530/eje.0.1390552
[2] Johansen PB et al. Ipamorelin, a new growth-hormone-releasing peptide, induces longitudinal bone growth in rats. Growth Hormone & IGF Research. 1999;9(2):106-113. DOI:10.1054/ghir.1999.9998
[3] Andersen NB et al. The growth hormone secretagogue ipamorelin counteracts glucocorticoid-induced decrease in bone formation of adult rats. Growth Hormone & IGF Research. 2001;11(5):266-272.
[4] Svensson J et al. The GH secretagogues ipamorelin and GH-releasing peptide-6 increase bone mineral content in adult female rats. Journal of Endocrinology. 2000;165(3):569-577.
[7] Aagaard NK et al. Growth hormone and growth hormone secretagogue effects on nitrogen balance and urea synthesis in steroid treated rats. Growth Hormone & IGF Research. 2009;19(5):426-431.
[8] Venkova K et al. Efficacy of ipamorelin, a novel ghrelin mimetic, in a rodent model of postoperative ileus. Journal of Pharmacology and Experimental Therapeutics. 2009;329(3):1110-1116.
[9] Greenwood-Van Meerveld B et al. Efficacy of ipamorelin, a ghrelin mimetic, on gastric dysmotility in a rodent model of postoperative ileus. Journal of Experimental Pharmacology. 2012;4:149-155.
[10] Beck DE, Sweeney WB, McCarter MD. 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):1527-1534. DOI:10.1007/s00384-014-2030-8
[11] Johansen PB et al. Pharmacokinetic evaluation of ipamorelin and other peptidyl growth hormone secretagogues with emphasis on nasal absorption. Xenobiotica. 1998;28(11):1083-1091.
[12] Gobburu JV et al. Pharmacokinetic-Pharmacodynamic Modeling of Ipamorelin, a Growth Hormone Releasing Peptide, in Human Volunteers. Pharmaceutical Research. 1999;16(9):1412-1416.
[15] GHS-R1a agonists anamorelin and ipamorelin inhibit cisplatin-induced weight loss in ferrets. Physiology & Behavior. 2024;284:114644. DOI:10.1016/j.physbeh.2024.114644
[16] U.S. FDA. Bulk Drug Substance Nomination: Ipamorelin acetate / Ipamorelin free base (FDA-2024-N-4188). 2024.
[17] Ishida J et al. Growth hormone secretagogues: history, mechanism of action, and clinical development. JCSM Rapid Communications. 2020;3(1):25-37.
[18] Sport Integrity Australia. Ipamorelin (Pentapeptide) Substance Information. 2025.

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