Ipamorelin

Dosing from the Literature

Published for growth hormone: IV doses from Phase 1 studies in healthy men. Not published: any trial of the under-the-skin doses people use.

The published trials gave ipamorelin by IV infusion: a Phase 1 study in healthy men (Gobburu et al., 1999) and a Phase 2 trial after bowel surgery (Beck et al., 2014). It is sold for injection under the skin. The last column of each row names where its figures come from.

What It Is

Ipamorelin is a synthetic pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH₂) that selectively activates the ghrelin / growth hormone secretagogue receptor (GHS-R1a), driving pulsatile growth hormone (GH) release from the pituitary. It was identified and characterized at Novo Nordisk's GH Biology department under development code NNC 26-0161 and first described by Raun and colleagues in a landmark 1998 paper in the European Journal of Endocrinology. The structural design started from GHRP-1 and removed the central Ala-Trp dipeptide (a chain of 2 amino acids); the resulting pentapeptide retained potent GH-releasing activity but, critically, lost the off-target hypothalamic-pituitary-adrenal (HPA) activation that plagued earlier GHRPs.

The compound's defining feature is selectivity. In pig studies and subsequent human data, ipamorelin releases GH with potency comparable to GHRP-6 and similar efficacy, but — unlike GHRP-6, GHRP-2, or hexarelin — does not raise plasma ACTH, cortisol, prolactin, FSH, LH, or TSH, even at doses >200× the ED50 for GH release. Raun's concluding sentence, now three decades old, still describes the compound's market position: "ipamorelin is the first GHRP-receptor agonist with a selectivity for GH release similar to that displayed by GHRH (the signal that tells the pituitary to release GH)."

Clinical development was pursued by Novo Nordisk, then licensed to Helsinn Therapeutics for postoperative ileus. A Phase 2 proof-of-concept trial (Beck, Sweeney, McCarter; Ipamorelin 201 Study Group, 2014) enrolled 114 bowel-resection patients randomized to ipamorelin 0.03 mg/kg IV twice daily for up to 7 days vs placebo. The compound was well tolerated, but the primary efficacy endpoint missed statistical significance (median time to first tolerated meal 25.3 vs 32.6 hours, p = 0.15). A second, larger Phase 2 trial (NCT01280344; 320 patients, three IV dose regimens) was completed in 2014 and has no posted or published results; no later trial of ipamorelin is registered. Ipamorelin was never submitted for FDA approval and today exists almost entirely as a research chemical and peptide-clinic compound.

Mechanism of Action

Ipamorelin is a selective agonist of the ghrelin receptor (GHS-R1a), binding the same receptor as GHRP-2, GHRP-6 and MK-677 (Sinha et al., 2020). The receptor is coupled to Gq/i proteins (Sigalos & Pastuszak, 2018), and GH secretagogues act through it at the pituitary and, mainly, the hypothalamus (the brain's hormonal control center) (Ghigo et al., 2001).

• GHS-R1a agonism (pituitary somatotrope) — The receptor activates phospholipase C (Sigalos & Pastuszak, 2018), and two other agonists at it, GHRP-6 and MK-677, raise calcium inside the cell (Sinha et al., 2020). Ipamorelin released GH from rat pituitary cells (Raun et al., 1998). Raun (1998) reported an in vivo ED50 of 2.3 ± 0.03 nmol/kg in conscious swine with a peak plasma GH ~65 ng/mL.
• Central synergy with GHRH — GH pulses are thought to be started by GHRH and amplified by GHRPs (synthetic GH triggers) (Veldhuis & Keenan, 2008). Given together, GHRH and a GHRP release GH synergistically (Sigalos & Pastuszak, 2018). No study has tested ipamorelin with Modified GRF (1-29) or CJC-1295.
• Somatostatin-sensitive — Somatostatin inhibits GH pulses (Veldhuis & Keenan, 2008). GHRPs release GH without disturbing the normal negative feedback from somatostatin and IGF-1, which, a review notes, can prevent supra-therapeutic GH levels (Sigalos & Pastuszak, 2018).
• Selectivity (what ipamorelin does NOT do) — Raun's selectivity work is the mechanistic foundation of ipamorelin's entire clinical identity. In swine, ipamorelin did not raise ACTH or cortisol above the levels seen after GHRH, even at more than 200 times its ED50 for GH release, and did not change FSH, LH, prolactin or TSH (Raun et al., 1998). This contrasts with GHRP-6 and GHRP-2, which raised ACTH and cortisol in the same study (Raun et al., 1998) and, for GHRP-2, prolactin, ACTH and cortisol in six healthy young adults (Arvat et al., 1997), and with MK-677 / ibutamoren, which raised prolactin in trials reviewed by Sinha et al. (2020) and cortisol over a year in healthy older adults (Nass et al., 2008).
• Pulsatile, not tonic — In healthy men given 15-minute IV infusions, plasma half-life was about 2 hours, and each dose produced a single GH episode that peaked at 0.67 hours (about 40 minutes) and declined to negligible levels (Gobburu et al., 1999).
• Bone-formation effect (preclinical) — Svensson et al. (2000) showed that 12-week continuous SC infusion of ipamorelin (0.5 mg/kg/day) in adult female rats increased total-body and regional bone mineral content (BMC) as measured by DXA, with increased ash weight and increased femoral/vertebral volume. Bone mineral content relative to body weight, and volumetric bone density, did not change: the bones grew larger (Svensson et al., 2000). No human bone data exist.
• GI motility (the ileus hypothesis) — Ghrelin-receptor stimulation has pro-motility effects in the upper and lower gastrointestinal tract (Beck et al., 2014). In rats after abdominal surgery, IV ipamorelin sped gastric emptying (Greenwood-Van Meerveld et al., 2012). In the published Phase 2 trial in 114 bowel-resection patients, the first tolerated meal came at a median 25.3 hours on ipamorelin vs 32.6 on placebo, not a significant difference (Beck et al., 2014).

What the Research Shows

Ipamorelin's published evidence base is small but internally consistent: preclinical work establishes potent, selective GH release and a favorable side-effect profile; Phase 1 human PK/PD work confirms the GH response; Phase 2 in postoperative ileus was negative on the primary endpoint.

• Discovery and preclinical potency (Raun 1998) — Ipamorelin released GH from primary rat pituitary cells with EC50 = 1.3 ± 0.4 nmol/L and Emax = 85 ± 5% of GHRP-6. In conscious swine, ED50 = 2.3 ± 0.03 nmol/kg, Emax 65 ± 0.2 ng GH/mL. GHRP-2 had higher potency (ED50 = 0.6 nmol/kg) but lower efficacy, and both GHRP-2 and GHRP-6 elevated ACTH and cortisol. Ipamorelin did not (Eur J Endocrinol 139:552-561).
• Phase 1 human PK/PD (Gobburu 1999) — Five ascending intravenous infusion rates (4.21, 14.02, 42.13, 84.27, 140.45 nmol/kg over 15 minutes), 8 healthy male subjects per dose. Linear pharmacokinetics, two-compartment PK model, dose-dependent GH pulse; at every dose, a single GH episode peaked at 0.67 hours (about 40 minutes) and declined to negligible levels. No ACTH or cortisol change (Pharm Res 16:1412-1416).
• Phase 1 multiple-ascending dose (Rasmussen 1998, abstract) — Randomized, double-blind, placebo-controlled, parallel-group, dose-escalation study in healthy subjects. Repeat dosing up to 7 days was well-tolerated; adverse event rates were comparable to placebo; sustained GH secretion response without desensitization over the dosing window (Growth Horm IGF Res 8:332, abstract).
• Preclinical bone formation (Svensson 2000) — 12-week continuous ipamorelin (0.5 mg/kg/day via osmotic minipump) in adult female Sprague-Dawley rats increased total-body BMC, tibia BMC, and vertebral (L3-L6) BMC relative to vehicle control. Effect comparable in magnitude to GHRP-6 at equivalent dose; both less than the rhGH (recombinant human growth hormone — the injectable pharmaceutical version) positive control but without the rhGH confounders. Femur and vertebral volumes were also increased (J Endocrinol 165:569-577).
• Preclinical ileus (Greenwood-Van Meerveld et al.) — Rodent postoperative ileus model showed improved gastric dysmotility with ipamorelin. Motivated the Helsinn Phase 2.
• Phase 2 postoperative ileus (Beck et al. 2014) — Randomized, placebo-controlled, multicenter proof-of-concept trial. 114 patients undergoing bowel resection, ipamorelin 0.03 mg/kg IV BID up to 7 days. Safety population: AE rate 87.5% (ipamorelin) vs 94.8% (placebo). Efficacy: median time to first tolerated meal 25.3 h vs 32.6 h (p = 0.15); time to first bowel movement numerically shorter but not significant. The compound was well tolerated but did not reach efficacy threshold; subsequent development terminated (Int J Colorectal Dis 29:1527-1534).
• Community and wellness-clinic "evidence" — Substantial practitioner reporting on ipamorelin + CJC-1295 or ipamorelin + Modified GRF (1-29) protocols for body composition, sleep quality, recovery, and aesthetic endpoints. These are uncontrolled and selection-biased, and are not evidence of efficacy on these endpoints. They are, at best, a description of how the peptide is being used.

Human Data

Consolidating the human evidence:

• Phase 1 PK/PD — Gobburu et al. 1999 (IV ascending dose, N = 40, healthy men) and Rasmussen et al. 1998 (single-dose + MAD, healthy subjects). Confirmed dose-dependent GH release, linear PK, ~2-hour plasma half-life, no ACTH/cortisol elevation, excellent short-term tolerability.
• Phase 2 postoperative ileus — Beck et al. 2014 (ClinicalTrials.gov NCT00672074). Helsinn-sponsored multicenter trial. N = 114 (modified intent-to-treat). Primary endpoint (time to first tolerated meal) missed statistical significance. Safety signal favorable.
• No obesity / body-composition / anti-aging RCTs — Despite widespread off-label use, ipamorelin has never been evaluated in a randomized, controlled trial for body composition, fat loss, lean-mass preservation, sleep, or "anti-aging" endpoints.
• No long-term safety data — The longest published human exposure is the 7-day Helsinn trial. Chronic multi-month use (common in wellness-clinic practice) has no published safety data.

Reconstitution & Storage

Sellers list ipamorelin as a lyophilized (freeze-dried) powder, in vials of 2, 5 and 10 mg among other sizes.

• Reconstitution — A clinic's storage guide describes adding the bacteriostatic water slowly down the inside wall of the vial, then swirling gently rather than shaking.
• Storage — Seller and clinic listings disagree. Clinic guides list the mixed solution at 2–8°C for 28–30 days, not frozen, and the powder as keeping 12–24 months refrigerated or 2 years or more at –20°C. A research-reagent seller lists the powder as stable for 3 weeks at room temperature but stored below –18°C, and the mixed solution as keeping 2–7 days at 4°C.
• Co-injection with GHRH analogs — Guides describe drawing ipamorelin and Modified GRF (1-29) into the same syringe; one clinic advises against mixing peptides in a syringe and sells the two pre-blended in one vial instead. No study has tested the two mixed.
• Inspection — A clinic's storage guide describes discarding a solution that turns cloudy or discolored, shows particles or smells unusual.
• Injection technique — A clinic's guide describes an insulin syringe, a pinched fold of skin on the abdomen at least two inches from the navel and cleaned with alcohol, the needle at 45 degrees, a slow push, and alternating sides of the abdomen.

→ Calculator — vial-to-syringe math

Side Effects & Risks

In the published Phase 2 trial, 87.5% of patients on ipamorelin and 94.8% on placebo had an adverse event (Beck et al., 2014). FDA, listing ipamorelin acetate among bulk substances that may present significant safety risks, cites serious adverse events, including death, in a published study of IV ipamorelin for gastric motility, and says it has found no safety information for certain other injectable routes (FDA Category 2 safety-risk list, April 2026). Risks listed below include documented, theoretical, and chronic-use extrapolations.

• Injection-site reactions — Clinic and guide pages list reactions where it is injected, such as redness or discomfort. The published trials gave it by IV infusion (Gobburu et al., 1999; Beck et al., 2014).
• Flushing, headache, head rush — Clinic and guide pages list headache, flushing and "head rush".
• Hunger / transient appetite increase — GH secretagogues stimulate food intake (Ghigo et al., 2001), and guide pages list increased hunger with ipamorelin. In mice injected twice daily for 9 weeks, ipamorelin raised food intake in the first week, and the weight gain came only in the first 1–2 weeks (Sinha et al., 2020, reviewing a mouse study).
• Sleep architecture — GH secretagogues influence sleep patterns (Ghigo et al., 2001). Guide pages list vivid dreams with ipamorelin, and a telehealth clinic's guide mentions disrupted sleep.
• No meaningful cortisol / ACTH / prolactin elevation (in swine) — This is the headline selectivity finding. In swine, ipamorelin did not raise ACTH or cortisol above the levels seen after GHRH, even at more than 200 times its ED50 for GH release, and did not change prolactin (Raun et al., 1998). By contrast, GHRP-6 and GHRP-2 raised ACTH and cortisol in the same study (Raun et al., 1998), and GHRP-2 and hexarelin raised prolactin, ACTH and cortisol in six healthy young adults (Arvat et al., 1997).
• Chronic IGF-1 elevation (theoretical) — A 2020 review counts ipamorelin among the GH secretagogues it calls potent GH and IGF-1 stimulators (Sinha et al., 2020); a year of MK-677 brought IGF-1 to young-adult levels in healthy older adults (Nass et al., 2008). Studies have linked exogenous GH use and higher IGF-1 levels with an increased risk of cancer, and long-term safety studies of GH secretagogues, including cancer incidence, are still needed (Sigalos & Pastuszak, 2018).
• Insulin sensitivity — A review of GH secretagogues reports that the IGF-1 rise they cause lowers insulin sensitivity and can raise blood glucose (Sigalos & Pastuszak, 2018). In healthy older adults, a year of MK-677 raised fasting glucose by an average 0.3 mmol/L (5 mg/dL) and lowered insulin sensitivity (Nass et al., 2008).
• Water retention / peripheral edema — Clinic and guide pages list water retention and tingling or numbness in the hands. With MK-677, another ghrelin-receptor agonist, transient mild lower-leg edema was among the most frequent side effects in healthy older adults (Nass et al., 2008).
• Purity / contamination — Ipamorelin is sold as a research chemical, not an approved drug. FDA says compounded ipamorelin acetate may pose a risk of immune reactions for certain routes, from aggregation or peptide-related impurities, and that its unnatural amino acids complicate characterizing the peptide (FDA Category 2 safety-risk list, April 2026).
• Anti-doping — Ipamorelin is prohibited at all times under WADA Section S2 (Peptide Hormones and Growth Factors) as a growth hormone secretagogue.
• Drug interactions — No interaction study in people has been published. In theory, somatostatin analogs (octreotide, lanreotide) would blunt its GH response, since somatostatin inhibits GH pulses (Veldhuis & Keenan, 2008).
• No data in pregnancy, breastfeeding, pediatrics — The published human studies enrolled healthy men and adults having bowel surgery (Gobburu et al., 1999; Beck et al., 2014).

Quick Compare — Ipamorelin vs GHRP-2 vs GHRP-6 vs MK-677

All four compounds are ghrelin-receptor (GHS-R1a) agonists. They differ in potency, selectivity, administration route, and — most importantly — their off-target endocrine effects.

Practical interpretation:

• Selectivity is the headline — Ipamorelin's defining property is that it releases GH without raising ACTH, cortisol, or prolactin. GHRP-2 and GHRP-6 don't; MK-677 partially doesn't.

→ See full MK-677 profile  •  → See full GHRP-2 profile  •  → See full GHRP-6 profile

Bloodwork & Monitoring

No trial, label or guideline sets monitoring for ipamorelin. A 2018 review of GH secretagogues as a class recommends following body composition, IGF-1, blood glucose and HbA1c during treatment (Sigalos & Pastuszak, 2018). The ipamorelin trials measured GH and ipamorelin levels in healthy men (Gobburu et al., 1999) and tracked adverse events and laboratory tests in surgical patients (Beck et al., 2014).

Commonly Stacked With

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→ Calculator — vial-to-syringe math

Legal Status

Related Compounds

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References

1. Raun K, Hansen BS, Johansen NL, Thøgersen H, Madsen K, Ankersen M, Andersen PH. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998;139(5):552-561. PMID: 9849822. (The foundational discovery paper; establishes the selectivity claim.)
2. Gobburu JVS, Agersø H, Jusko WJ, Ynddal L. Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharm Res. 1999;16(9):1412-1416. PMID: 10496658.
3. Rasmussen MH, Søgaard B, Ynddal L, et al. Ipamorelin — a novel very potent growth hormone secretagogue. Growth Horm IGF Res. 1998;8(4):332. DOI: 10.1016/s1096-6374(98)80212-8. (Abstract P-11).
4. Svensson J, Lall S, Dickson SL, Bengtsson BA, Rømer J, Ahnfelt-Rønne I, Ohlsson C, Jansson JO. The GH secretagogues ipamorelin and GH-releasing peptide-6 increase bone mineral content in adult female rats. J Endocrinol. 2000;165(3):569-577. PMID: 10828840.
5. Beck DE, Sweeney WB, McCarter MD; Ipamorelin 201 Study Group. Prospective, randomized, controlled, proof-of-concept study of the Ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients. Int J Colorectal Dis. 2014;29(12):1527-1534. PMID: 25331030.
6. Greenwood-Van Meerveld B, Tyler K, Mohammadi E, Pietra C. Efficacy of ipamorelin, a ghrelin mimetic, on gastric dysmotility in a rodent model of postoperative ileus. J Exp Pharmacol. 2012;4:149-155. PMID: 27186127.
7. Hansen BS, Raun K, Nielsen KK, Johansen PB, Hansen TK, Peschke B, et al. Pharmacological characterization of a new oral GH secretagogue, NN703. Eur J Endocrinol. 1999;141(2):180-189. PMID: 10427162. (Novo Nordisk GHS chemistry context.)
8. Ishida J, Saitoh M, Ebner N, Springer J, Anker SD, von Haehling S. Growth hormone secretagogues: history, mechanism of action, and clinical development. JCSM Rapid Commun. 2020;3(1):25-37. doi: 10.1002/rco2.9.
9. Sigalos JT, Pastuszak AW. The Safety and Efficacy of Growth Hormone Secretagogues. Sex Med Rev. 2018;6(1):45-53. PMID: 28400207.
10. Bowers CY. Unnatural growth hormone-releasing peptide begets natural ghrelin. J Clin Endocrinol Metab. 2001;86(4):1464-1469. PMID: 11297568.
11. Kojima M, Hosoda H, Date Y, Nakazato M, Matsuo H, Kangawa K. Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature. 1999;402(6762):656-660. PMID: 10604470. (Endogenous ligand at the GHS-R1a receptor that ipamorelin mimics.)
12. Ghigo E, Arvat E, Giordano R, et al. Biologic activities of growth hormone secretagogues in humans. Endocrine. 2001;14(1):87-93. PMID: 11322506.
13. Arvat E, Di Vito L, Maccagno B, et al. Effects of GHRP-2 and hexarelin, two synthetic GH-releasing peptides, on GH, prolactin, ACTH and cortisol levels in man. Comparison with the effects of GHRH, TRH and hCRH. Peptides. 1997;18(6):885-891. PMID: 9285939.
14. Sinha DK, Balasubramanian A, Tatem AJ, Rivera-Mirabal J, Yu J, Kovac J, et al. Beyond the androgen receptor: the role of growth hormone secretagogues in the modern management of body composition in hypogonadal males. Transl Androl Urol. 2020;9(Suppl 2):S149-S159. PMID: 32257855.
15. Veldhuis JD, Keenan DM. Secretagogues govern GH secretory-burst waveform and mass in healthy eugonadal and short-term hypogonadal men. Eur J Endocrinol. 2008;159(5):547-554. PMID: 18703567.
16. Nass R, Pezzoli SS, Oliveri MC, Patrie JT, Harrell FE Jr, Clasey JL, et al. Effects of an oral ghrelin mimetic on body composition and clinical outcomes in healthy older adults. Ann Intern Med. 2008;149(9):601-611. PMID: 18981485. (MK-677 comparator data.)
17. ClinicalTrials.gov. Study of IPAMORELIN on the Management of Postoperative Ileus Following Partial Bowel Resection. NCT00672074.
18. World Anti-Doping Agency. The 2026 Prohibited List. Section S2 — Peptide Hormones, Growth Factors, Related Substances and Mimetics. wada-ama.org.
19. U.S. Food and Drug Administration. Bulk Drug Substances That Raise Significant Safety Risks (Category 2) Under Section 503A / 503B. FDA.gov. Updated 2025.
20. FDA. Bulk Drug Substances Nominated for Use in Compounding Under Section 503A of the FD&C Act (503A categories list), versions updated April 15, April 22 and May 14, 2026. fda.gov/media/94155/download. Read October 3, 2026. (Notice that 12 peptides would leave Category 2 because their nominations were withdrawn; their removal; GHK-Cu, except injectable, back in Category 1.)
21. Stone W. The wellness world is eager for RFK Jr.’s promised move on peptides. NPR, March 31, 2026. npr.org/2026/03/31/nx-s1-5768206/peptides-rfk-fda-compounding-pharmacies. Read October 3, 2026. (The HHS secretary’s late-February podcast remarks, “about 14” peptides; reported, not a rule.)
22. Lu Z, Ngan MP, Liu JYH, Yang L, Tu L, Chan SW, Giuliano C, Lovati E, Pietra C, Rudd JA. 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. Physiol Behav. 2024;284:114644. PMID: 39043357. DOI: 10.1016/j.physbeh.2024.114644.

Related Research

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• GH StackCJC-1295 · Ipamorelin — pulsatile growth hormone protocol
• FDA TrackerPCAC voted on 7 of the 12 peptides on July 23–24, 2026; FDA plans a PCAC review of the other 5 before the end of February 2027.