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Ipamorelin

Tier 2 · Preclinical
Also known as NNC 26-0161

The strongest evidence present is Tier 1 human RCT/PK data: a human pharmacokinetic study in healthy male subjects (n=8 per dose level), a Phase I dose-ranging study, and a prospective randomized Phase II proof-of-concept trial for postoperative ileus. However, higher-tier sources agree human efficacy data are very thin — limited to small PK/PD studies and one discontinued/failed Phase II trial — with the majority of evidence deriving from rodent and swine models. Body-composition, sleep, bone and anti-aging benefit claims appear only in tier-3 vendor/clinic material and are explicitly noted as never tested in humans.

Half-life
~2 h
Routes
Subcutaneous · Intravenous · Intramuscular · Intranasal (animal studies) · Oral (animal studies)
Goals
Growth hormone / IGF-1 stimulation · Body composition · Recovery / tissue repair · Sleep (claimed) · Gastrointestinal motility (investigational)
Cost / mg
$20

How it works

Vendor and educational profiles describe ipamorelin (NNC 26-0161) as a synthetic five-amino-acid peptide that mimics the natural hunger hormone ghrelin by switching on the ghrelin receptor (GHSR-1a) in the pituitary gland and hypothalamus. According to these sources, this prompts the pituitary to release a pulse of growth hormone (GH), which in turn raises IGF-1 and is said to drive protein synthesis, fat breakdown and tissue repair. What multiple profiles emphasize is its selectivity: animal studies reported that ipamorelin releases GH without raising cortisol, prolactin, ACTH or other pituitary hormones, and expert commentary notes it does so while preserving the body's natural pulsatile GH rhythm rather than flooding the system with a constant elevation.

Overview

Overview

Vendor and educational profiles describe ipamorelin (research designation NNC 26-0161) as a synthetic pentapeptide ghrelin receptor (GHSR-1a) agonist and selective growth hormone (GH) secretagogue, with the structure Aib-His-D-2-Nal-D-Phe-Lys-NH2 (src-1, src-4, src-5, src-9, src-10, src-13, src-18). These sources report a molecular formula of C38H49N9O5, a molecular weight cited variously as 711.85, 711.86 or 711.9 g/mol, CAS number 170851-70-4, and PubChem CID 9831659 (src-4, src-5, src-7, src-9, src-10, src-11).

Vendor profiles and a review state that ipamorelin was first described by researchers at Novo Nordisk in the mid-to-late 1990s, with foundational characterization published by Raun et al. in 1998, and describe it as a third-generation growth hormone-releasing peptide (src-4, src-5, src-6, src-7, src-9, src-10, src-12, src-13).

Reported Mechanism

Animal studies characterized ipamorelin as the first GHRP-receptor agonist with selectivity for GH release similar to GHRH, identified within a series of compounds lacking the central Ala-Trp dipeptide of GHRP-1, and acting via a GHRP-6-like receptor (src-18, src-1). In vitro studies using primary rat pituitary cells reported GH release with an EC50 of 1.3 ± 0.4 nmol/L and an Emax of 85 ± 5% (src-1, src-4, src-18). Preclinical studies reported GH release in anaesthetised rats with an ED50 of 80 ± 42 nmol/kg and in conscious swine with an ED50 of 2.3 ± 0.03 nmol/kg (src-18, src-13).

A notable selectivity finding: animal studies reported that ipamorelin released GH with potency comparable to GHRP-6 but did not release ACTH, cortisol, FSH, LH, prolactin or TSH even at doses more than 200-fold higher than the GH-releasing ED50, whereas GHRP-6 and GHRP-2 raised ACTH and cortisol (src-5, src-13, src-18). Multiple profiles describe ipamorelin as amplifying pulsatile GH secretion that preserves the natural rhythm and negative feedback rather than producing a flat elevation as seen with exogenous GH (src-5, src-6, src-11, src-12, src-13). huddlemenshealth states that ipamorelin reduces the inhibitory signal from somatostatin and that the resulting GH surge raises IGF-1, driving protein synthesis, lipolysis and tissue repair (src-14, src-17).

Human Clinical Evidence

A human RCT/PK study in 8 healthy male subjects per dose level reported dose-proportional kinetics and a single episode of GH release peaking at 0.67 hours, declining exponentially to negligible levels at all doses (src-15, src-1). peptidebreakdown reports that in a Phase I study, intravenous ipamorelin (0.01–1 μg/kg) produced dose-dependent GH release in healthy male volunteers, with GH peaking approximately 40 minutes post-injection and returning to baseline within 2–3 hours; at the highest dose cortisol and prolactin remained unchanged from baseline (src-6, src-20).

The only completed efficacy program was a prospective, randomized, controlled Phase II proof-of-concept study for management of postoperative ileus in patients undergoing partial bowel resection, at doses of 0.03 mg/kg BID, 0.06 mg/kg BID and 0.06 mg/kg TID by intravenous infusion (src-2, src-3). ClinicalTrials.gov describes the trial as enrolling 320 patients across 45 locations, ages 18-85 and weight 40-150 kg, with a primary outcome of gastrointestinal function recovery up to 10 days post-operatively; it started April 2011 with study completion May 2014 (src-3, src-13, src-2). Note that source counts differ: PeptideGarden and superpower.com describe the completed Phase II RCT as n=114 (licensed by Helsinn Therapeutics) and report that it failed to meet its primary endpoint, with human efficacy data outside this trial absent (src-7, src-13, src-1, src-6); the sources do not reconcile the 320 vs 114 figures, and the tier-1 trial source frames it as a proof-of-concept study without stating failure. peptpedia states human data is limited to two PK/PD studies and a discontinued Phase II trial, with the majority of evidence deriving from rodent models (src-12).

Animal Findings

Animal studies report a range of effects: a rodent postoperative ileus model where a single 1 mg/kg dose decreased time to first bowel movement and repetitive dosing increased fecal output, food intake and body weight (src-30); attenuation of colonic hypersensitivity and somatic allodynia in rats via a ghrelin-receptor-mediated mechanism blocked by antagonist H0900 (src-28); dose-dependent increases in longitudinal bone growth rate in female rats (from 42 to 52 µm/day) without affecting total IGF-I, IGFBPs or bone turnover markers (src-26); and increased somatotroph secretion-granule density after chronic treatment (src-29). Pepteligence reports GH hypersecretion in streptozotocin-diabetic mice alongside reduced hepatic IGF-I mRNA, and increased fat pad weights suggesting possible GH-independent effects on adiposity (src-1). A review reported that CJC-1295 combined with ipamorelin improved maximum tetanic tension in murine glucocorticoid-induced muscle loss, while concluding current evidence does not support clinical use for orthopaedic applications (src-19).

Reported Uses and Claims

A review describes ipamorelin as a potent GH and IGF-1 stimulator that can improve body composition and ameliorate hypogonadal symptoms, while noting clinical efficacy data for GH secretagogues largely remain lacking (src-21); another notes such secretagogues were developed to treat GH deficiency (src-8). Lower-tier sources go further: Paragon Sports Medicine asserts (framed as clinical studies) that ipamorelin increases lean muscle mass, may reduce adipose tissue, may enhance slow-wave sleep and may increase bone mineral density (src-9), and huddlemenshealth adds largely anecdotal claims of improved recovery, body composition, stamina, sleep and anti-aging (src-14). These human benefit claims appear only in tier-3 vendor/clinic material and are explicitly contradicted by PeptideGarden's note that body composition, anti-aging and sleep claims have never been tested in humans (src-7).

mypeptidematch describes ipamorelin as commonly combined with the GHRH analog CJC-1295, whose pathways are said to converge synergistically (src-11).

What the research shows

264 findings extracted from the 31 sources cited below, strongest evidence first within each group. Every one links to the source it came from.

What human studies found

Based on 11 human trial findings, 3 human study findings, 18 animal findings, 15 expert opinion findings, 6 anecdotal findings and 1 theoretical finding.

  • human trialIpamorelin induces a single episode of GH release with peak at 0.67 hours1

  • human trialGH concentration declines exponentially to negligible levels after ipamorelin administration at all doses1

  • human trialIpamorelin induces GH release at all dose levels tested1

  • human trialPrimary outcome assessed recovery of gastrointestinal function up to 10 days post-operatively2

  • human trialIpamorelin was studied in a prospective, randomized, controlled, proof-of-concept study for management of postoperative ileus in bowel resection patients3

  • human trialOutside of a phase II randomized controlled trial in postoperative ileus, human efficacy data are absent4

  • human trialThe compound failed its only completed efficacy trial25

  • human trialPhase II RCT (n=114) for postoperative ileus failed its primary endpoint25

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  • human trialHelsinn Therapeutics licensed ipamorelin and attempted to develop it for postoperative ileus but the Phase II trial failed to show significant efficacy25

  • human trialPreclinical data available; one failed Phase 2 RCT (postoperative ileus, 2014)26

  • human trialIn a Phase I study, intravenous ipamorelin (0.01–1 μg/kg) produced dose-dependent GH release in healthy male volunteers29

  • human studyA small-scale study suggests that ipamorelin may contribute to organ health, especially the digestive system23

  • human studyIn human studies it raised GH without meaningfully elevating cortisol or prolactin24

  • human studyIpamorelin produced GH release comparable to GHRP-6 at equivalent doses, but without the cortisol spike29

  • animalIpamorelin demonstrated efficacy in a rodent model of postoperative ileus3

  • animalCJC-1295 combined with ipamorelin showed significantly improved maximum tetanic tension in murine models with glucocorticoid-induced muscle loss7

  • animalIpamorelin administered i.p. (1-3 mg/kg) did not affect cisplatin-induced acute or delayed emesis in ferrets10

  • animalIpamorelin administered i.p. (1-3 mg/kg) inhibited cisplatin-induced weight loss on the last day of delayed phase (48-72 h) by approximately 24%10

  • animalIpamorelin significantly attenuated colonic hypersensitivity in rats with non-inflammatory visceral hypersensitivity induced by dilute acetic acid11

  • animalIpamorelin significantly attenuated somatic mechanical allodynia in rats11

  • animalA single dose of ipamorelin (1 mg/kg) decreased the time to the first bowel movement compared with vehicle in a rodent model of postoperative ileus14

  • animalA single dose of ipamorelin (1 mg/kg) had no effect on cumulative fecal output, food intake, or body weight gain measured 48 h after surgery14

  • animalRepetitive dosing of ipamorelin (0.1 or 1 mg/kg) significantly increased cumulative fecal pellet output, food intake, and body weight gain in a rodent model of postoperative ileus14

  • animalIpamorelin dose-dependently increased longitudinal bone growth rate (LGR) from 42 microm/day in the vehicle group to 44, 50, and 52 microm/day in the treatment groups16

  • animalIpamorelin had a pronounced and dose-dependent effect on body weight gain16

  • animalNNC 26-0235 shows comparable in vivo potency to ipamorelin, GHRP-2, and GHRP-6 following iv administration17

  • animalIpamorelin was able to increase basal GH level by more than 10-fold after oral administration17

  • animalSeveral compounds show high in vivo potency and efficacy in anesthetized rats17

  • animalIn glucocorticoid-treated rats mimicking osteoporosis, Ipamorelin counteracted steroid-induced bone loss by enhancing bone formation without changing bone mineral density markers24

  • animalAnimal studies show consistent demonstration of selective GH release in swine and rats, with additional bone growth and GI motility studies25

  • animalIpamorelin's defining pharmacological advantage, established in a 1998 study, is GH stimulation without elevating cortisol, ACTH, or prolactin26

  • animalSelective GH stimulation without cortisol or prolactin elevation in animal models; its sole human RCT failed to meet its primary endpoint26

  • expert opinionCurrent evidence does not support the clinical use of ipamorelin for orthopaedic applications7

  • expert opinionSeveral peptide drugs have undergone rigorous approval processes that evaluate both safety and efficacy8

  • expert opinionTherapeutic peptides are a promising tool for treating type 2 diabetes and obesity, for skin rejuvenation, and as hormone analogs for specific diseases and conditions8

  • expert opinionDosing and pharmacokinetic parameters for CJC-1295/Ipamorelin combination have not been established in published human clinical trials20

  • expert opinionClinical studies demonstrate ipamorelin's efficacy in increasing lean muscle mass in healthy adults22

  • expert opinionResearch indicates potential benefits in reducing visceral and subcutaneous adipose tissue22

  • expert opinionPreclinical and clinical evidence supports enhanced slow-wave sleep duration and quality22

  • expert opinionStudies suggest potential benefits in increased bone mineral density and enhanced osteoblast activity22

  • expert opinionIpamorelin has only a handful of human studies, primarily pharmacokinetic trials and a discontinued Phase II for postoperative ileus24

  • expert opinionHuman data is limited to two PK/PD studies and a discontinued Phase II trial; the majority of evidence derives from rodent models24

  • expert opinionNo human data for body composition, anti-aging, or sleep25

  • expert opinionNo completed human efficacy trials for GH-related indications26

  • expert opinionIpamorelin represents an investigational peptide requiring rigorous validation through well-designed clinical trials to establish safety and efficacy for healthspan extension28

  • expert opinionIpamorelin can significantly improve body composition30

  • expert opinionCurrent data on clinical efficacy of growth hormone secretagogues including ipamorelin largely remain lacking30

  • anecdotalMost patients notice sleep improvements within 2–4 weeks; body composition changes typically emerge around weeks 8–1220

  • anecdotalIpamorelin increases protein synthesis and amino acid utilization for improved muscle development and recovery23

  • anecdotalIncreased GH secretion significantly improves body composition and helps the body more effectively metabolize stored fat, mainly targeting stubborn belly fat23

  • anecdotalOptimized hormone secretion boosts cellular function, increasing stamina and reducing fatigue23

  • anecdotalSome patients report improved sleep patterns after peptide injections, supporting recovery and hormone balance23

  • anecdotalBetter sleep and recovery often appear in 2-4 weeks; lean-muscle and body-fat changes build gradually over 8-12 weeks23

  • theoreticalSelectivity of Ipamorelin has been confirmed in multiple preclinical and clinical investigations, as documented in research published in the Journal of Clinical Endocrinology and Metabolism (Raun et al., 1998)31

How it works

Based on 5 human trial findings, 3 human study findings, 29 animal findings, 15 in vitro findings, 36 expert opinion findings and 20 theoretical findings.

  • human trialIpamorelin is a growth hormone releasing peptide1

  • human trialIpamorelin is a ghrelin mimetic3

  • human trialGhrelin is an appetite-stimulatory signal from stomach with structural resemblance to motilin3

  • human trialGhrelin enhances appetite and increases food intake in humans3

  • human trialIpamorelin raises GH without spiking cortisol or prolactin, demonstrating selectivity unlike older compounds in its class25

  • human studyGhrelin influences interdigestive gastrointestinal motility in humans3

  • human studyIpamorelin acts as an agonist at the ghrelin receptor (GHSR-1a) in the pituitary gland, stimulating the release of growth hormone through activation of specific signaling pathways24

  • human studyIpamorelin raises GH without significantly affecting cortisol, prolactin, or ACTH at standard doses29

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  • animalGhrelin stimulates gastric acid secretion and motility in rats3

  • animalIpamorelin was characterized as the first selective GHS, showing minimal stimulation of cortisol, prolactin, or ACTH release in preclinical models4

  • animalAnimal studies indicate that chronic ipamorelin treatment alters somatotroph cell populations and GH content in rat pituitary tissue4

  • animalAnimal studies indicate that ipamorelin acts as a peripherally restricted ghrelin receptor agonist capable of attenuating visceral and somatic pain in experimental models4

  • animalIn streptozotocin-diabetic mice, intravenous ipamorelin induced GH hypersecretion (GH levels 150 ± 35 µg/L versus 62 µg/L in controls) alongside reduced hepatic IGF-I mRNA expression4

  • animalIpamorelin stimulated GH secretion with potency comparable to GHRP-6 but did not produce significant increases in adrenocorticotropic hormone (ACTH), cortisol, or prolactin at effective GH-releasing doses5

  • animalIn the foundational study by Raun et al. (1998), ipamorelin released GH with an ED50 comparable to GHRP-6 in swine, but did not affect ACTH or cortisol levels even at doses up to 200-fold above the GH-releasing ED505

  • animalIpamorelin amplifies pulsatile GH secretion rather than producing a tonic elevation5

  • animalIpamorelin stimulates GH secretion in preclinical models without producing concurrent elevations in adrenocorticotropin (ACTH), cortisol, prolactin, thyroid-stimulating hormone (TSH), or the gonadotropins FSH and LH6

  • animalIpamorelin inhibited EFS-induced contractions of isolated ferret ileum by 54.4% with IC=11.7 µM10

  • animalIpamorelin is a peripherally restricted ghrelin receptor agonist11

  • animalThe anti-nociceptive effects of ipamorelin were blocked by ghrelin receptor antagonist H0900, indicating ghrelin receptor-mediated mechanism11

  • animalGhrelin receptor-mediated mechanisms are involved in visceral and somatic hypersensitivity in the absence of active colonic inflammation11

  • animalIpamorelin is a selective growth hormone secretagogue and agonist of the ghrelin receptor14

  • animalGhrelin and ghrelin mimetics stimulate appetite and enhance gastric motility14

  • animalIpamorelin is a GH secretagogue (GHS) that can exert a considerable effect on GH secretion15

  • animalChronic treatment with Ipamorelin over 21 days in young female rats increased the volume density of secretion granules in somatotroph cells (P<0.05)15

  • animalIn the Ipamorelin group, basal intracellular GH content in somatotroph cells over 4 hours was lower than in the saline control group15

  • animalIpamorelin exerts a dynamic control effect on the somatotroph population and on GH hormone content in young female rats15

  • animalIpamorelin is a new and potent synthetic pentapeptide which has distinct and specific growth hormone (GH)-releasing properties16

  • animalIpamorelin treatment did not affect total IGF-I levels, IGFBPs, or serum markers of bone formation and resorption16

  • animalThe number of tartrate-resistant acid phosphatase-positive multinuclear cells in the metaphysis of the tibia did not change significantly with treatment16

  • animalPituitary GH content was unchanged by ipamorelin treatment16

  • animalIpamorelin displays high GH releasing potency and efficacy in vitro and in vivo18

  • animalIn pentobarbital anaesthetised rats, ipamorelin released GH with ED50 = 80+/-42 nmol/kg and Emax = 1545+/-250 ng GH/ml18

  • animalIn conscious swine, ipamorelin released GH with ED50 = 2.3+/-0.03 nmol/kg and Emax = 65+/-0.2 ng GH/ml plasma18

  • animalIpamorelin is the first GHRP-receptor agonist with selectivity for GH release similar to that displayed by GHRH18

  • animalIpamorelin peptide could be easily transported across nasal epithelium19

  • animalIpamorelin demonstrates potency comparable to GHRP-6 but without the ACTH, cortisol, FSH, LH, prolactin, or TSH elevations seen with earlier GHRPs even at doses 200-fold above the GH-release ED5026

  • in vitroIpamorelin is a synthetic pentapeptide ghrelin receptor (GHSR1a) agonist and selective growth hormone secretagogue4

  • in vitroIn vitro studies using rat pituitary cells demonstrated that ipamorelin stimulates GH release with an EC50 of 1.3 ± 0.4 nmol/L and an Emax of 85 ± 5%4

  • in vitroIpamorelin binds to GHS-R1a on somatotroph cells of the anterior pituitary, stimulating GH release through a phospholipase C-dependent intracellular calcium signaling pathway5

  • in vitroIn pituitary cell assays, ipamorelin has demonstrated an EC50 of approximately 1.3 nM, indicating high potency at the GHSR6

  • in vitroUpon GHSR-1a engagement in in vitro pituitary preparations, ipamorelin activates Gαq/11-coupled phospholipase C (PLC), generating inositol trisphosphate (IP3) and diacylglycerol (DAG)6

  • in vitroGly-Ipamorelin was identified as an analogue of GHRP, representing Ipamorelin extended by a N-terminal glycine residue13

  • in vitroIn pituitary cell cultures from Ipamorelin-treated rats, in vitro Ipamorelin treatment at 10(-8) M for 4 hours increased the percentage of somatotroph cells15

  • in vitroOnly in the Ipamorelin-treated group did Ipamorelin, GHRP 6, and GHRH treatment prompt increased intracellular GH content15

  • in vitroIpamorelin is a GH secretagogue17

  • in vitroSeveral compounds from ipamorelin-derived series release GH with high in vitro potency and efficacy in rat pituitary cell assay17

  • in vitroIpamorelin is a pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH2)18

  • in vitroIpamorelin was identified within a series of compounds lacking the central dipeptide Ala-Trp of GHRP-118

  • in vitroIn vitro, ipamorelin released GH from primary rat pituitary cells with potency EC50 = 1.3+/-0.4 nmol/l and Emax = 85+/-5%18

  • in vitroIpamorelin stimulates GH release via a GHRP-like receptor, similar to GHRP-618

  • in vitroElectrophysiological studies of isolated somatotroph cells demonstrate that Ipamorelin induces characteristic calcium oscillations and membrane depolarization patterns consistent with pulsatile growth hormone release31

  • expert opinionIpamorelin is a growth hormone secretagogue (GHS) that acts as an agonist of the growth hormone secretagogue receptor (GHS-R)12

  • expert opinionIpamorelin, as a ghrelin receptor agonist, mimics the actions of ghrelin in stimulating GH secretion12

  • expert opinionGHRPs are short (3-6 amino acids long) peptides with GH releasing properties13

  • expert opinionCJC-1295 and ipamorelin work on different but complementary receptors to coax your pituitary gland into releasing more of your own growth hormone — in pulses that closely resemble your body's natural secretion pattern, rather than the flat pharmacological spike you'd get from exogenous HGH20

  • expert opinionCJC-1295 is a synthetic analog of growth hormone-releasing hormone (GHRH), the signal your hypothalamus sends when it wants your pituitary to produce GH20

  • expert opinionIpamorelin is a growth hormone secretagogue (GHS) that works through the ghrelin receptor (GHSR-1a) — a separate pathway that amplifies the GH pulse20

  • expert opinionGH is naturally secreted in pulses during slow-wave sleep, and dosing in this window is thought to amplify rather than override that rhythm20

  • expert opinionThe rapid clearance reflects the peptide's enzymatic degradation and renal elimination pathways21

  • expert opinionIpamorelin is a synthetic pentapeptide consisting of 5 amino acids (Aib-His-D-2-Nal-D-Phe-Lys-NH2) classified as a growth hormone secretagogue receptor (GHSR) agonist22

  • expert opinionIpamorelin represents one of the most selective growth hormone-releasing peptides (GHRPs) available, demonstrating minimal activation of secondary hormone pathways compared to other compounds in its class22

  • expert opinionIpamorelin's selectivity for GH release, without significantly affecting cortisol, prolactin, or acetylcholine pathways, distinguishes it from other growth hormone secretagogues22

  • expert opinionIpamorelin selectively binds to and activates GHSR-1a receptors, leading to enhanced cyclic adenosine monophosphate (cAMP) production and increased protein kinase A (PKA) activation22

  • expert opinionThe peptide promotes endogenous hormone release through pulsatile growth hormone secretion mimicking natural circadian rhythms22

  • expert opinionIpamorelin influences cellular metabolism by enhancing lipolysis through hormone-sensitive lipase activation22

  • expert opinionIpamorelin is a pentapeptide compound and a growth hormone releasing peptide that functions as a selective growth hormone secretagogue, stimulating the pituitary gland to release more human growth hormones23

  • expert opinionIpamorelin mimics the natural hormone ghrelin and prompts your body to secrete more of its own growth hormone (GH)23

  • expert opinionIpamorelin binds to growth-hormone secretagogue receptors (GHS-R) in the hypothalamus and pituitary, reduces the inhibitory signal from somatostatin, and triggers a rapid GH pulse23

  • expert opinionGH surge raises circulating insulin-like growth factor 1 (IGF-1), which drives protein synthesis, lipolysis, and tissue repair23

  • expert opinionIpamorelin delivers both immediate and follow-on GH pulses that promote cell regeneration, lean-mass gains, and metabolic vitality23

  • expert opinionIpamorelin is a pentapeptide growth hormone secretagogue that stimulates the pituitary via the ghrelin receptor24

  • expert opinionIpamorelin is called the first truly selective growth hormone secretagogue because it stimulates GH release without measurably raising cortisol, prolactin, or ACTH at therapeutic doses24

  • expert opinionIpamorelin preserves the natural pulsatile rhythm of growth hormone release rather than forcing a continuous elevation, maintaining normal feedback regulation24

  • expert opinionIpamorelin is a synthetic pentapeptide growth hormone secretagogue that acts as a selective agonist at the ghrelin receptor (GHSR-1a)24

  • expert opinionFirst described by Raun et al. in 1998, it is distinguished from other GHRPs by releasing GH without meaningfully elevating cortisol, prolactin, or ACTH at therapeutic doses24

  • expert opinionThe peptide stimulates GH release in a dose-dependent manner while maintaining the natural pulsatile pattern of GH secretion24

  • expert opinionIpamorelin is a synthetic growth hormone secretagogue that tells the pituitary gland to release growth hormone25

  • expert opinionIpamorelin is a fully synthetic pentapeptide that mimics ghrelin and binds to the GHS-R1a receptor on pituitary cells25

  • expert opinionOlder growth hormone secretagogues like GHRP-6 and GHRP-2 raise cortisol, prolactin, and aldosterone as collateral effects, while ipamorelin does not25

  • expert opinionIpamorelin is a synthetic pentapeptide that activates the GHS-R1a receptor to stimulate pulsatile growth hormone release26

  • expert opinionA synthetic pentapeptide that selectively activates the growth hormone secretagogue receptor (GHS-R1a) to stimulate pulsatile GH release26

  • expert opinionIpamorelin works by binding to and activating the growth hormone secretagogue receptor subtype 1a, designated GHS-R1a26

  • expert opinionIpamorelin mimics ghrelin interaction by binding GHS-R1a on somatotroph cells in the anterior pituitary, triggering the release of growth hormone in a pulsatile pattern that preserves the hypothalamic feedback mechanisms governing GH secretion26

  • expert opinionGHRP-6 raises cortisol and provokes significant hunger, unlike ipamorelin29

  • expert opinionGHRP-2 can elevate both cortisol and prolactin, unlike ipamorelin29

  • expert opinionIpamorelin's ghrelin-mimetic mechanism is distinct from GHRH analogs like CJC-1295 and sermorelin, which act on GHRH receptors, and these two pathways converge synergistically29

  • expert opinionIpamorelin is a potent GH and IGF-1 stimulator30

  • theoreticalIpamorelin exerts its effects primarily through activation of the growth hormone secretagogue receptor type 1a (GHS-R1a), also known as the ghrelin receptor5

  • theoreticalIpamorelin is structurally characterized as Aib-His-D-2-Nal-D-Phe-Lys-NH26

  • theoreticalIpamorelin stimulates growth hormone (GH) release by engaging the GH secretagogue receptor (GHSR-1a) in the pituitary and hypothalamus6

  • theoreticalThe molecular weight of ipamorelin is 711.9 g/mol6

  • theoreticalIpamorelin acts as a selective agonist at the growth hormone secretagogue receptor type 1a (GHSR-1a), a G-protein-coupled receptor expressed primarily on somatotroph cells of the anterior pituitary and on neurons of the arcuate nucleus of the hypothalamus6

  • theoreticalGrowth hormone secretagogues like ipamorelin activate IGF-1 signaling and satellite cell repair9

  • theoreticalIpamorelin is a ghrelin mimetic10

  • theoreticalIpamorelin is a synthetic five-amino-acid peptide that stimulates growth hormone release29

  • theoreticalIpamorelin belongs to the growth hormone-releasing peptide (GHRP) family, which mimics ghrelin by binding to the GHS-R1a receptor on pituitary cells29

  • theoreticalIpamorelin binds to the ghrelin receptor (GHS-R1a) on pituitary somatotroph cells and triggers a signaling cascade involving phospholipase C activation, inositol triphosphate (IP3) production, intracellular calcium release, and ultimately GH vesicle exocytosis29

  • theoreticalIpamorelin produces pulsatile release of growth hormone that amplifies the body's natural GH secretion pattern without fundamentally altering it29

  • theoreticalUnlike exogenous GH injection, ipamorelin works within the body's feedback system and GH pulses remain physiological in shape with preserved negative feedback mechanisms29

  • theoreticalIpamorelin (NNC 26-0161) represents a third-generation growth hormone-releasing peptide (GHRP) distinguished by its high selectivity for the growth hormone secretagogue receptor type 1a (GHS-R1a)31

  • theoreticalIpamorelin demonstrates selective growth hormone (GH) secretion without concurrent elevation of adrenocorticotropic hormone (ACTH), cortisol, or prolactin31

  • theoreticalThe molecular structure of Ipamorelin (Aib-His-D-2-Nal-D-Phe-Lys-NH2) incorporates strategic amino acid modifications that confer enhanced metabolic stability and receptor selectivity31

  • theoreticalIpamorelin belongs to the growth hormone secretagogue class of bioactive peptides, specifically categorized as a ghrelin mimetic31

  • theoreticalIpamorelin functions as a selective agonist at the growth hormone secretagogue receptor type 1a (GHS-R1a), a G protein-coupled receptor (GPCR) predominantly expressed in somatotroph cells of the anterior pituitary gland31

  • theoreticalReceptor binding initiates intracellular signaling cascades primarily mediated through Gq/11 proteins, resulting in activation of phospholipase C (PLC), generation of inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG), and subsequent mobilization of intracellular calcium stores31

  • theoreticalIpamorelin exhibits minimal cross-reactivity with receptors mediating cortisol, prolactin, or ACTH secretion31

  • theoreticalThe resulting elevation in intracellular calcium concentration ([Ca2+]i) from approximately 100 nM to 500-1000 nM represents the critical trigger for growth hormone secretory vesicle fusion with the plasma membrane31

Dosing

Based on 1 human trial finding, 2 human study findings, 1 animal finding, 3 expert opinion findings and 1 anecdotal finding.

  • human trialIpamorelin was evaluated at doses of 0.03 mg/kg BID, 0.06 mg/kg BID, and 0.06 mg/kg TID via intravenous infusion2

  • human studyNo published human dosing or safety guidance exists beyond a small pharmacokinetic study (n=8 per dose level)4

  • human studyAt standard doses (~1 μg/kg), ipamorelin produces a robust GH pulse with no measurable increase in cortisol, prolactin, or ACTH29

  • animalIpamorelin was administered intravenously in the experimental model11

  • expert opinionInformation regarding the indications, dosing, frequency, and duration of treatment with ipamorelin remains unknown7

  • expert opinionTypical dosing is 200-300 µg once before bed23

  • expert opinionMost men run it alongside weekly testosterone shots for 3- to 6-month cycles23

  • anecdotalThe most commonly reported clinical protocol pairs 200–300 mcg of ipamorelin with 200–300 mcg of CJC-1295 (with DAC), injected subcutaneously 3–5 times per week, typically 30–60 minutes before sleep20

How the body handles it

Based on 6 human trial findings, 7 human study findings, 9 animal findings, 1 in vitro finding, 13 expert opinion findings and 2 theoretical findings.

  • human trialIpamorelin shows dose-proportionality in pharmacokinetic parameters1

  • human trialIpamorelin has a short terminal half-life of 2 hours1

  • human trialIpamorelin clearance is 0.078 L/h/kg1

  • human trialIpamorelin volume of distribution at steady-state is 0.22 L/kg1

  • human trialPhase I PK/PD studies confirmed selective GH release25

  • human trialGH peaked approximately 40 minutes post-injection and returned to baseline within 2–3 hours29

  • human studyHuman pharmacokinetic data from a controlled study demonstrate a short terminal half-life of approximately 2 hours and dose-proportional kinetics across a range of intravenous doses4

  • human studyTime to peak plasma concentration (Tmax) occurs within approximately 15-30 minutes after SC administration5

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  • human studyThe subcutaneous bioavailability of small peptides in this molecular weight range (711.85 Da) is generally high, estimated at 65-95%5

  • human studyAfter intravenous administration of 1 μg/kg, ipamorelin produced measurable GH peaks within 15-20 minutes5

  • human studyThe volume of distribution at steady state was estimated at approximately 0.2-0.4 L/kg, consistent with a hydrophilic peptide that distributes primarily into the extracellular fluid compartment with limited tissue penetration5

  • human studySubcutaneous Tmax is 15-30 minutes, with peak plasma ipamorelin concentrations followed by a terminal elimination half-life of approximately 2 hours24

  • human studyGH release begins within 10 minutes of administration, peaks at 30-40 minutes, and returns to baseline by approximately 3 hours24

  • animalThe N-terminal α-aminoisobutyric acid (Aib) residue resists proteolytic degradation relative to natural amino acids, extending the half-life of the peptide in biological systems examined in preclinical studies6

  • animalPlasma GH response was marginally reduced after ipamorelin treatment16

  • animalPlasma GH response was unchanged after GHRH in ipamorelin-treated animals16

  • animalNNC 26-0235 demonstrated 10% oral bioavailability in dogs17

  • animalIpamorelin demonstrates systemic plasma clearance 5-fold lower than that of GHRP-6 following i.v. bolus injection19

  • animalIpamorelin was mainly excreted in the urine19

  • animalIpamorelin showed moderate resistance towards metabolism with 60-80% of administered dose recovered from bile and urine as intact peptide19

  • animalAfter intranasal application, bioavailability of ipamorelin was approximately 20%19

  • animalIpamorelin is a synthetic pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH2) that released GH in conscious swine with an ED50 of 2.3 ± 0.03 nmol/kg and an Emax of 65 ± 0.2 ng/mL plasma26

  • in vitroEstablished in-vitro experiments provided preliminary information considering the potential metabolism of Gly-Ipamorelin after administration13

  • expert opinionCJC-1295 with DAC has a significantly longer half-life (approximately 6–8 days — though that figure hasn't been established in published human clinical data)20

  • expert opinionThe non-DAC version (also called Modified GRF 1-29) has a much shorter half-life and is typically used for more precise pulse timing20

  • expert opinionIpamorelin: ~2 hours, though half-life not established in humans20

  • expert opinionIpamorelin exhibits remarkably rapid GH secretion initiation with observable increases in growth hormone levels occurring within minutes of peptide delivery21

  • expert opinionIntravenous delivery typically produces measurable effects within 5-15 minutes21

  • expert opinionSubcutaneous or intramuscular administration may require 15-30 minutes for peak responses21

  • expert opinionMaximum GH responses typically manifest 30-60 minutes following Ipamorelin administration, depending on dose and route21

  • expert opinionMost research protocols observe significant GH elevation for 60-120 minutes post-administration, with gradual decline thereafter as the body metabolises the compound21

  • expert opinionIpamorelin demonstrates a relatively short biological half-life, typically ranging from 60-90 minutes in most research models21

  • expert opinionThe peptide is metabolized primarily through peptidase enzymes and eliminated through renal excretion, with metabolites detectable for up to 24 hours post-administration22

  • expert opinionHalf-life: Approximately 2 hours (plasma elimination)22

  • expert opinionPlasma half-life of roughly two hours23

  • expert opinionNo accumulation occurs with repeated dosing24

  • theoreticalIpamorelin is metabolized primarily through enzymatic degradation by ubiquitous peptidases, including dipeptidyl peptidase-IV (DPP-IV), aminopeptidases, and carboxypeptidases present in plasma, liver, and kidney5

  • theoreticalThe strategic incorporation of D-amino acids at positions 3 and 4 prevents rapid enzymatic degradation by endogenous peptidases31

Safety and side effects

Based on 3 human trial findings, 2 human study findings, 5 animal findings, 13 expert opinion findings and 1 anecdotal finding.

  • human trialSecondary outcomes investigated ancillary GI functions and safety/tolerability including adverse events, laboratory and clinical parameters2

  • human trialPhase II trial (n=114) provides the largest safety dataset and was well-tolerated at 0.03 mg/kg BID for up to 7 days25

  • human trialAt the highest dose tested in Phase I, cortisol and prolactin remained unchanged from baseline29

  • human studyIt does not significantly stimulate ACTH, cortisol, or prolactin release at physiological doses24

  • human studyAt doses that produce substantial GH release, ipamorelin does not significantly elevate cortisol, prolactin, or ACTH29

  • animalThe ultrastructure of somatotroph cells did not change with Ipamorelin treatment15

  • animalIpamorelin did not affect FSH, LH, PRL or TSH plasma levels in swine18

  • animalGHRP-6 and GHRP-2 resulted in increased plasma levels of ACTH and cortisol, but ipamorelin did not release ACTH or cortisol at levels significantly different from GHRH stimulation18

Show the remaining 16

  • animalIpamorelin lacked effect on ACTH and cortisol even at doses more than 200-fold higher than ED50 for GH release18

  • animalEven at doses >200-fold above its ED50 for GH release, ipamorelin does not significantly elevate ACTH or cortisol25

  • expert opinionIpamorelin is currently on the WADA Prohibited List4

  • expert opinionFurther studies are needed before most new peptides can be used safely in humans8

  • expert opinionNeither peptide is FDA approved as a standalone drug, but both are legally available in the US through licensed compounding pharmacies by prescription20

  • expert opinionPromotes cellular regeneration without increasing cortisol or other hormones23

  • expert opinionUnlike GHRP-6 and GHRP-2, ipamorelin does not elevate plasma cortisol or ACTH at growth hormone-releasing doses24

  • expert opinionNo significant prolactin elevation occurs, eliminating the gynecomastia concerns associated with GHRP-2 at higher doses24

  • expert opinionNo ghrelin-mimetic appetite stimulation — unlike GHRP-6, which produces intense hunger within minutes of injection24

  • expert opinionNo FAERS data — no post-marketing surveillance exists25

  • expert opinionAs of September 2023, the FDA classified ipamorelin as a Category 2 bulk drug substance, prohibiting its use in compounded medications for human administration26

  • expert opinionIpamorelin has never received FDA approval for any indication26

  • expert opinionIpamorelin is an unapproved peptide operating largely outside of regulatory oversight27

  • expert opinionUnapproved peptides like ipamorelin demonstrate outcomes in animal models but rigorous human safety data are scarce27

  • expert opinionIpamorelin lacks long-term safety data and systematic validation compared to FDA-approved peptide agents28

  • anecdotalSide effects are generally mild and dose-dependent: water retention, joint aches, and transient injection-site reactions are the most common20

What people use it for

Based on 1 human trial finding, 1 human study finding, 5 animal findings, 11 expert opinion findings, 2 anecdotal findings and 1 theoretical finding.

  • human trialPost-operative administration of ipamorelin is expected to reduce time to recovery of Gastrointestinal (GI) function in patients who have undergone partial small and/or large bowel resection2

  • human studyIpamorelin has been investigated in Phase II clinical trials for post-surgical gastrointestinal recovery but has not received regulatory approval for any indication5

  • animalAnimal studies suggest GH-independent effects on adiposity: ipamorelin increased fat pad weights relative to body weight in both GH-deficient and GH-intact mouse models4

  • animalAnimal studies indicate that ipamorelin inhibited cisplatin-induced weight loss in ferrets at doses of 1–3 mg/kg administered intraperitoneally4

  • animalIpamorelin has been investigated in preclinical research contexts spanning GH-axis modulation, gastrointestinal motility, musculoskeletal physiology, and metabolic endocrinology6

  • animalThe compound is commonly studied in combination with the synthetic GHRH analog CJC-12956

  • animalPostsurgical intravenous infusions of ipamorelin may ameliorate symptoms in patients with postoperative ileus14

  • expert opinionIpamorelin is among the most popular types of injectable peptide therapy being marketed to patients for orthopaedic injuries7

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  • expert opinionTherapeutic peptides are short chains of amino acids used to treat metabolic and endocrine conditions such as obesity and type 2 diabetes8

  • expert opinionNovel, unapproved compounds have emerged and are rapidly expanding into preventive medicine and performance enhancement8

  • expert opinionGrowth hormone secretagogues including ipamorelin have been developed to treat growth hormone deficiency, which causes growth retardation, gastrointestinal dysfunction, and altered body composition12

  • expert opinionIpamorelin's rapid clearance allows for sequential administrations within a single study day, enabling researchers to conduct multiple rounds of testing on individual subjects without waiting extended washout periods21

  • expert opinionBody composition claims have never been tested in humans25

  • expert opinionIpamorelin is a peptide marketed direct to patients in the gray market27

  • expert opinionIpamorelin is identified as a peptide with applications in growth hormone modulation28

  • expert opinionIpamorelin was developed by Novo Nordisk in the 1990s and reached Phase II clinical trials for post-operative ileus but was not commercialized29

  • expert opinionIpamorelin is not FDA-approved for any human therapeutic use29

  • expert opinionIpamorelin can ameliorate hypogonadal symptoms including fat gain and muscular atrophy30

  • anecdotalThe combination is most commonly used for body composition, recovery acceleration, and sleep quality20

  • anecdotalIpamorelin can help reduce visible signs of aging, leading to fewer wrinkles and improved skin elasticity23

  • theoreticalIpamorelin is a growth hormone secretagogue9

Other findings

Based on 2 in vitro findings, 4 expert opinion findings and 5 theoretical findings.

  • in vitroThe structure of Gly-Ipamorelin was characterised by means of high resolution (tandem) mass spectrometry13

  • in vitroThe identity of Gly-Ipamorelin was confirmed by custom synthesis13

  • expert opinionOriginally developed by Novo Nordisk in the late 1990s22

  • expert opinionStable in aqueous solution when refrigerated, susceptible to degradation at room temperature22

  • expert opinionIpamorelin was developed by Novo Nordisk in Denmark in the mid-1990s25

  • expert opinionIpamorelin is also referred to by its Novo Nordisk research designation NNC 26-016126

  • theoreticalIpamorelin is a synthetic pentapeptide growth hormone secretagogue originally developed by Novo Nordisk in the late 1990s5

  • theoreticalIpamorelin is a synthetic pentapeptide growth hormone secretagogue first described by researchers at Novo Nordisk in the late 1990s6

Show the remaining 3

  • theoreticalIpamorelin in the 2X Blend has been tested to 99.6% purity (Lot YPB.238)6

  • theoreticalIpamorelin is supplied as a lyophilized (freeze-dried) white powder6

  • theoreticalThe molecular weight of Ipamorelin is 711.86 g/mol31

Points of contention

Where the evidence is unsettled, thin, or says less than the popular claim — worth knowing before you draw conclusions.

Contested

Trial participant count differs between sources.

ClinicalTrials.gov (NCT01280344) lists 320 actually enrolled patients for the phase II postoperative ileus trial, while PeptideGarden and superpower.com describe the completed Phase II RCT as n=114. Sources do not reconcile these figures.

Contested

Trial outcome framed as both proof-of-concept and outright failure.

The tier-1 trial source (Prospective, randomized, controlled, proof-of-concept study of the Ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients) describes a prospective proof-of-concept study without stating failure, while PeptideGarden and superpower.com state the sole Phase II RCT failed to meet its primary endpoint and was not commercialized.

Limited evidence

Human efficacy evidence is very thin.

Higher-tier sources agree human data is limited to a small PK study (n=8/dose), two PK/PD studies, and one discontinued/failed Phase II trial; the majority of evidence is from rodent and swine models. No human GH-indication efficacy trials have been completed.

Single source

Human body-composition, sleep, bone and anti-aging benefits come only from low-tier vendor/clinic sources.

Claims that ipamorelin increases lean muscle mass, reduces adipose tissue, enhances slow-wave sleep, improves skin/anti-aging, and increases bone mineral density in humans appear only in tier-3 vendor/clinic material (Paragon, huddlemenshealth) framed as clinical studies, and are explicitly contradicted by PeptideGarden's note that such claims have never been tested in humans.

Limited evidence

Some PK figures are extrapolated, not measured for ipamorelin.

PeptideInsight's subcutaneous bioavailability estimate of 65-95% is stated as a general estimate for small peptides in this molecular-weight range rather than a measured ipamorelin value; several kinetic figures are described as not established in published human data.

Using it with other compounds

Check a stack
  • TesamorelinSame downstream effect

    May be complementary

    Tesamorelin is a stabilized GHRH analog acting on the GHRH receptor — a distinct mechanism from ipamorelin's ghrelin receptor — but both raise GH/IGF-1 and support fat loss. Combining a GHRH-side driver with ipamorelin's ghrelin-side amplification produces a larger GH pulse, and tesamorelin's specific strength in reducing visceral fat can complement ipamorelin's reported lipolysis for body-composition goals.

    Tier 2Supported by animal / early studies

    What the research doesn't fully establish

    The mechanism descriptions clearly establish that both peptides converge on shared downstream pathways despite distinct receptor targets. Ipamorelin acts via GHSR-1a (ghrelin receptor) while tesamorelin acts via GHRHR (GHRH receptor)—these are indeed different upstream mechanisms. However, both demonstrably activate the GH_axis (pulsatile GH release from anterior pituitary somatotrophs), both elevate IGF-1 (ipamorelin via GH→IGF-1 signaling; tesamorelin via hepatic JAK2/STAT5 induction), both engage cAMP_PKA signaling (ipamorelin explicitly lists cAMP/PKA; tesamorelin's Gs-alpha/adenylate cyclase/cAMP pathway activates PKA), and both produce lipolysis effects. The shared_downstream relationship type is justified: the peptides use different receptors but converge on common effector pathways and biological outcomes. The four claimed shared dimensions (GH_axis, IGF1_signaling, cAMP_PKA, lipolysis) are all explicitly supported in the mechanism material for both peptides. The explanation accurately describes the complementary nature of their distinct mechanisms feeding into overlapping downstream biology.

    Timing Administer together on an empty stomach; nighttime dosing aligns with natural GH pulses.

    Shares GH axis · IGF1 signaling · cAMP PKA · lipolysis

  • SermorelinSame downstream effect

    May be complementary

    Sermorelin is a GHRH-receptor agonist, a different upstream pathway from ipamorelin's ghrelin receptor, but both feed into the same GH/IGF-1 axis. Pairing a GHRH analog with a ghrelin-receptor agonist is the well-known two-pronged strategy: sermorelin drives GHRH-side signaling while ipamorelin adds the ghrelin-side push and blunts somatostatin, giving a bigger combined GH pulse while keeping the release pulsatile.

    Tier 2Supported by animal / early studies

    What the research doesn't fully establish

    The mechanism descriptions clearly establish that both peptides converge on the GH/IGF-1 axis despite different upstream targets. Ipamorelin targets GHSR-1a (ghrelin receptor) and sermorelin targets GHRH receptor—distinct receptors. However, both pathways lead to pulsatile GH release and IGF-1 elevation. The shared dimensions are well-justified: (1) GH_axis—both explicitly stimulate GH secretion via different receptor pathways; (2) IGF1_signaling—both increase IGF-1 as a downstream effect of elevated GH; (3) cAMP_PKA—ipamorelin's mechanism includes 'cAMP / protein kinase A (PKA)' and sermorelin's explicitly uses 'Gs/adenylyl cyclase/cAMP' and is tagged with 'cAMP_PKA'. The explanation correctly identifies them as complementary upstream inputs (ghrelin-side vs. GHRH-side) that converge on common downstream GH secretion and IGF-1 signaling. This is a classic example of same_downstream relationship where different receptor agonists feed into the same physiological axis.

    Timing Dose together, on an empty stomach, typically at night to match endogenous GH rhythm.

    Shares GH axis · IGF1 signaling · cAMP PKA

  • TirzepatideStack with caution

    Worth caution

    Ipamorelin activates the ghrelin receptor (GHS-R1a), which can mildly stimulate appetite — the opposite of tirzepatide's central appetite reduction. While ipamorelin is relatively selective and its appetite effect is modest, the two pull in opposite directions on hunger signaling and this is worth understanding before combining.

    Tier 4Theoretical — not established

    What the research doesn't fully establish

    The mechanism descriptions clearly establish opposing effects on appetite regulation. Tirzepatide's mechanisms explicitly include 'Appetite reduction' and 'Hypothalamic appetite/satiety signaling' via GLP-1R and GIP receptor activation. Ipamorelin's mechanisms describe activation of the ghrelin receptor (GHSR-1a), which is the natural hunger hormone receptor. The explanation correctly identifies that these represent opposing directions on hunger signaling—tirzepatide suppresses appetite while ipamorelin activates the hunger hormone pathway. This mechanistic opposition justifies the 'caution' relationship type, even though no shared dimensions are claimed. The proposed relationship is grounded in the actual, opposing mechanisms described for both peptides.
  • MK-677Same mechanism

    Worth caution

    MK-677 (ibutamoren) is an oral non-peptide that hits the same ghrelin receptor (GHS-R1a) as ipamorelin. Running both means competing for the identical receptor and GH-release pathway, so the effect is redundant rather than additive. MK-677 also produces a long, sustained receptor activation plus notable appetite stimulation and water retention — layering ipamorelin on top adds little extra GH while compounding those side effects. Most people should use one GHS-R1a agonist, not two.

    Tier 3Largely anecdotal — commonly discussed

    What the research doesn't fully establish

    Both peptides' mechanisms clearly establish they target the same receptor (GHS-R1a/GHSR-1a ghrelin receptor) and activate overlapping downstream pathways (Gq/11-coupled phospholipase C → IP3/intracellular calcium → GH-vesicle exocytosis). Both produce pulsatile GH secretion and IGF-1 elevation through the GH/IGF-1 axis. The shared dimensions (GH_axis, IGF1_signaling) are explicitly supported by both descriptions. The mechanism material confirms both are ghrelin receptor agonists operating through the same receptor and GH-release pathway, justifying the 'same_mechanism' classification and the claim of redundancy rather than additivity.

    Timing Pick one ghrelin-receptor agonist rather than stacking; MK-677's long half-life keeps the receptor occupied for many hours.

    Shares GH axis · IGF1 signaling

  • BPC-157Complementary

    No documented conflict

    BPC-157 upregulates the GH receptor and drives tissue repair through angiogenic/VEGFR2 and eNOS pathways, while ipamorelin raises circulating GH that can act on those upregulated receptors — a mechanistically complementary pairing often used anecdotally for recovery. Distinct mechanisms, shared repair/growth output.

    Tier 4Theoretical — not established
  • CJC-1295Complementary

    May be complementary

    Ipamorelin works through a different receptor (the ghrelin/GHS-R1a receptor) than CJC-1295's GHRH-R. GHRH analogs increase the size of each GH pulse while ghrelin-mimetics increase pulse frequency and suppress somatostatin — so the two amplify each other's GH release. This GHRH + GHRP pairing is the classic synergistic GH stack.

    Tier 3Largely anecdotal — commonly discussed

    What the research doesn't fully establish

    The mechanisms clearly establish complementary action on the GH_axis and IGF1_signaling. CJC-1295 targets GHRH-R and amplifies endogenous pulsatile GH secretion via cAMP-PKA pathways, increasing GH pulse amplitude. Ipamorelin targets GHSR-1a (ghrelin receptor) and triggers pulsatile GH release via Gαq/11-PLC and cAMP-PKA pathways. The proposed explanation that GHRH analogs increase pulse size while ghrelin-mimetics increase pulse frequency is mechanistically consistent with their distinct receptor targets and signaling cascades. Both converge on GH secretion and downstream IGF-1 signaling but through different physiological mechanisms (GHRH stimulation vs. ghrelin mimicry), making them complementary rather than redundant. The shared dimensions (GH_axis, IGF1_signaling) are explicitly supported by both peptides' documented effects and approved tags.

    Timing Commonly co-administered in the same injection, typically on an empty stomach at night.

    Shares GH axis · IGF1 signaling

  • AOD-9604Complementary

    May be complementary

    AOD-9604 drives fat mobilization through a GH-independent route (beta-3 adrenergic/HSL activation, not the GH receptor), while ipamorelin promotes lipolysis indirectly via GH release. Because they hit fat metabolism from different directions and both ultimately raise cAMP-driven hormone-sensitive lipase activity, they can be used together for fat-loss goals without receptor competition.

    Tier 4Theoretical — not established

    What the research doesn't fully establish

    Both peptides' mechanisms clearly establish the claimed shared dimensions and complementary relationship. (1) Lipolysis: Ipamorelin effects include 'Lipolysis (reported)' via 'Hormone-sensitive lipase / lipolysis' pathway; AOD-9604 effects include 'Stimulation of lipolysis (fat mobilization)' via 'Hormone-sensitive lipase activation, Lipolysis stimulation' pathway. (2) cAMP_PKA: Ipamorelin pathways include 'cAMP / protein kinase A (PKA)'; AOD-9604 pathways include 'Cyclic AMP (cAMP) elevation' and approved tag 'cAMP_PKA'. (3) Complementarity via different routes: The mechanisms confirm distinct pathways—ipamorelin acts through GHSR-1a → GH release → IGF-1 signaling → lipolysis, while AOD-9604 acts through beta-3 adrenergic receptor upregulation → cAMP elevation → HSL activation, explicitly stated as 'effect not directly receptor-mediated' and 'Does NOT meaningfully bind the classical hGH receptor.' The explanation's claim of 'GH-independent route' for AOD-9604 and indirect GH-mediated lipolysis for ipamorelin is directly supported by the provided mechanisms. No receptor competition is evident from the descriptions.

    Timing Both are often used fasted; no strict separation required.

    Shares lipolysis · cAMP PKA

  • HexarelinSame mechanism

    Worth caution

    Both hexarelin and ipamorelin are growth hormone secretagogues that switch on the exact same pituitary receptor (GHS-R1a) to trigger a GH pulse, so stacking them is largely redundant rather than additive — you're pushing the same button twice. The key difference is selectivity: hexarelin also raises ACTH, cortisol and prolactin and blunts (desensitizes) with continued use, whereas ipamorelin gives a cleaner GH pulse without those extra hormones. For most goals you'd choose one, and ipamorelin is the cleaner GHS-R1a option.

    Tier 2Supported by animal / early studies

    What the research doesn't fully establish

    Both peptides' mechanisms clearly establish they target the same receptor (GHS-R1a/GHSR-1a) and activate the same primary pathway (phospholipase C → IP3/intracellular calcium → GH exocytosis) to achieve pulsatile GH release and IGF-1 elevation. The shared dimension 'GH_axis' is explicitly documented in both mechanisms. The explanation accurately reflects the mechanism material: hexarelin's additional effects on ACTH/cortisol/prolactin are documented in its mechanism, while ipamorelin's mechanism explicitly states 'Selective GH secretion without ACTH/cortisol/prolactin release.' The characterization of functional redundancy on the primary GH-axis mechanism is justified by the identical receptor targeting and overlapping downstream signaling pathways described.

    Timing If both are on hand, use one per session rather than doubling up on the same receptor.

    Shares GH axis

Safety and side effects

Safety and Tolerability

Selectivity profile

Animal studies reported that ipamorelin released GH with potency comparable to GHRP-6 but did not release ACTH, cortisol, FSH, LH, prolactin or TSH even at doses more than 200-fold higher than the GH-releasing ED50 (src-5, src-13, src-18). peptidebreakdown reports that at the highest Phase I dose tested, cortisol and prolactin remained unchanged from baseline (src-6). Multiple profiles contrast ipamorelin with older secretagogues: GHRP-6 is said to raise cortisol and provoke significant hunger and GHRP-2 to elevate cortisol and prolactin, whereas ipamorelin is described as producing no significant prolactin elevation (eliminating gynecomastia concerns) and no ghrelin-mimetic appetite stimulation (src-6, src-7, src-12).

Human safety data

PeptideGarden reports that the Phase II trial (cited as n=114) provides the largest human safety dataset and was well-tolerated at 0.03 mg/kg BID for up to 7 days, and that the overall evidence base comprises roughly 3 human studies, ~120 subjects in safety data, and ~15 animal studies (src-7). Secondary outcomes of the trial investigated safety and tolerability including adverse events and laboratory and clinical parameters (src-3). PeptideGarden also notes there is no FAERS data and no post-marketing surveillance for ipamorelin (src-7).

Anecdotal sources report generally mild, dose-dependent side effects such as water retention, joint aches and transient injection-site reactions (src-11, src-14).

Regulatory status

  • superpower.com states that as of September 2023 the FDA classified ipamorelin as a Category 2 bulk drug substance, prohibiting its use in compounded medications for human administration, and that ipamorelin has never received FDA approval for any indication (src-13, src-6, src-5).
  • mypeptidematch states neither ipamorelin nor CJC-1295 is FDA approved as a standalone drug, but describes both as legally available in the US through licensed compounding pharmacies by prescription (src-11).
  • Ipamorelin is on the WADA Prohibited List; a glycine-extended metabolite (Gly-Ipamorelin) has been characterized by high-resolution tandem mass spectrometry in an anti-doping context (src-1, src-31).

Overall caveat

Multiple reviews describe ipamorelin as a gray-market, unapproved peptide operating largely outside regulatory oversight that demonstrates outcomes in animal models but lacks rigorous long-term human safety data and systematic validation, requiring well-designed clinical trials to establish safety and efficacy (src-20, src-23, src-24). Pepteligence states no published human dosing or safety guidance exists beyond the small PK study (n=8 per dose level), and a review notes indications, dosing, frequency and duration of treatment remain unknown (src-1, src-19).

Reconstitution and handling

Dosing

No dose has been established for this compound. Ipamorelin has never received FDA approval for any indication (per superpower.com, src-13), and Pepteligence states no published human dosing or safety guidance exists beyond a small pharmacokinetic study (n=8 per dose level), with a review noting indications, dosing, frequency and duration remain unknown (src-1, src-19). The figures below are what sources report — not guidance.

Doses used in research and reported protocols

  • The human PK study used 15-minute intravenous infusions at rates of 4.21, 14.02, 42.13, 84.27 and 140.45 nmol/kg (src-15, src-1).
  • The Phase I study used intravenous doses of 0.01–1 μg/kg (src-6).
  • The Phase II postoperative ileus trial used 0.03 mg/kg BID, 0.06 mg/kg BID, and 0.06 mg/kg TID by intravenous infusion (src-2, src-3).
  • Anecdotal/vendor sources report a commonly used protocol of 200–300 mcg ipamorelin paired with 200–300 mcg CJC-1295 (with DAC), injected subcutaneously 3–5 times per week 30–60 minutes before sleep, or ipamorelin 200-300 µg once before bed run over 3-6 month cycles, often alongside weekly testosterone; these sources explicitly note these parameters have not been established in published human clinical trials (src-11, src-14).

Reported onset and time course

  • peptideslabuk states IV delivery produces measurable effects within 5-15 minutes, subcutaneous/intramuscular within 15-30 minutes, peak GH at 30-60 minutes, and GH elevation lasting 60-120 minutes (src-16).
  • peptpedia states GH release begins within 10 minutes, peaks at 30-40 minutes and returns to baseline by ~3 hours, with plasma ipamorelin peaking at ~25 minutes and no accumulation with repeated dosing (src-12).
  • Profiles report a subcutaneous Tmax of ~15-30 minutes and a subcutaneous bioavailability estimated at 65-95% — noted as a general estimate for small peptides in this molecular-weight range rather than a measured ipamorelin value (src-5, src-12).
  • Anecdotal sources report sleep improvements within 2–4 weeks and body composition changes around weeks 8–12 (src-11, src-14).

Pharmacokinetics

The tier-1 human PK study reported dose-proportional kinetics, a terminal half-life of approximately 2 hours, clearance of 0.078 L/h/kg, and a volume of distribution at steady state of 0.22 L/kg (src-15, src-1). Profiles cite plasma elimination half-life of ~2 hours with metabolism primarily by peptidases, renal excretion, and metabolites detectable up to 24 hours (src-9, src-14, src-11); the ~2 hour figure is noted as not established in humans by mypeptidematch (src-11), and peptideslabuk cites a shorter 60-90 minute biological half-life in research models (src-16). Profiles state metabolism proceeds via ubiquitous peptidases including DPP-IV, aminopeptidases and carboxypeptidases, and that the N-terminal Aib residue and D-amino acids at positions 3 and 4 resist proteolytic degradation, extending half-life (src-4, src-5, src-10). An animal study reported systemic plasma clearance 5-fold lower than GHRP-6 after IV bolus in rats, ~20% bioavailability after intranasal application, and 60-80% of dose recovered as intact peptide (src-22).

Preparation and Storage

Vendor material reports the ipamorelin blend tested to 99.6% purity (Lot YPB.238), supplied as a lyophilized white powder described as stable refrigerated in aqueous solution (src-4, src-9). Reconstitution of a lyophilized peptide vial is typically performed with bacteriostatic water; the amount added determines the resulting concentration (for example, adding 2 mL to a 5 mg vial yields 2.5 mg/mL). Sources do not specify a standardized reconstitution volume for research use.

Sources

Ordered by evidence quality — the strongest first.

  1. Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers - PubMed(opens in a new tab)
    Tier 1Web · pubmed.ncbi.nlm.nih.gov
  2. Safety and Efficacy of Ipamorelin Compared to Placebo for the Recovery of Gastrointestinal Function(opens in a new tab)
    Tier 1Web · clinicaltrials.gov
  3. Prospective, randomized, controlled, proof-of-concept study of the Ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients(opens in a new tab)
    Tier 1Web · doi.org · 2014
  4. Ipamorelin: Mechanism, Dosing & Evidence (Tier 2) | Pepteligence(opens in a new tab)
    Tier 2Web · pepteligence.com · 2026
  5. Ipamorelin: Research Evidence & Safety Profile | PeptideInsight(opens in a new tab)
    Tier 2Web · peptideinsight.com · 2026
  6. Ipamorelin Research — Selective GH Secretagogue, Preclinical Studies & Safety Profile - Peptide.co(opens in a new tab)
    Tier 2Web · peptide.co · 2026
  7. Injectable Peptide Therapy: A Primer for Orthopaedic and Sports Medicine Physicians.(opens in a new tab)
    Tier 2PubMed · pubmed.ncbi.nlm.nih.gov · 2026
  8. Therapeutic Peptides in Aesthetic, Metabolic and Endocrine Conditions: Effects, Safety, Clinical Applications, and Future Perspectives.(opens in a new tab)
    Tier 2PubMed · pubmed.ncbi.nlm.nih.gov · 2026
  9. Therapeutic Peptides in Orthopaedics: Applications, Challenges, and Future Directions.(opens in a new tab)
    Tier 2PubMed · pubmed.ncbi.nlm.nih.gov · 2026
  10. The growth hormone secretagogue receptor 1a agonists, anamorelin and ipamorelin, inhibit cisplatin-induced weight loss in ferrets: Anamorelin also exhibits anti-emetic effects via a central mechanism.(opens in a new tab)
    Tier 2PubMed · pubmed.ncbi.nlm.nih.gov · 2024
  11. Attenuation of Visceral and Somatic Nociception by Ghrelin Mimetics.(opens in a new tab)
    Tier 2PubMed · pubmed.ncbi.nlm.nih.gov · 2020
  12. Growth hormone secretagogues: history, mechanism of action, and clinical development(opens in a new tab)
    Tier 2Web · doi.org · 2020
  13. Analysis of new growth promoting black market products.(opens in a new tab)
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