Ipamorelin

CNot approvedGH secretagogues (GHRPs) →GH secretagogueghrelin mimeticNNC 26-0161
In one paragraphIpamorelin is a synthetic five-amino-acid peptide that stimulates growth-hormone release with little effect on cortisol or prolactin. Small early studies confirmed the hormone release; the only randomised trial — 117 bowel-surgery patients, testing it for post-operative gut recovery — found no benefit, and development stopped. It is not an approved medicine anywhere, and the popular claims about muscle, fat loss and sleep have never been tested in a trial.
Schematic 3D structure of Ipamorelin
5 residues · pentapeptide · schematic
Overall gradeC Weak
Human trials1 RCT (negative) + small early-phase
Outcomes graded5
Last reviewed2 September 2026
EvidenceWhat it isHow it worksUnknownsMolecule & PKRegulationQuestionsReferences

What the human research shows

The peptide that shows how far marketing can drift from evidence. The pharmacology is real — it does release growth hormone, more selectively than older secretagogues. But the one proper trial failed on its endpoint, the developer walked away, and every claim made for it since rests on that pharmacology rather than on any measured outcome in people.

MetabolicCardioMuscleHealingNeuroImmuneSexualSkinAgeing

Evidence profile0–5

  • Metabolic & weight—0.0
  • Cardiovascular—0.0
  • Muscle & growthC1.3
  • Healing & repairC0.0
  • Neuro & sleepD0.0
  • Immune & inflammation—0.0
  • Sexual & hormonal—0.0
  • Skin & appearance—0.0
  • Ageing & longevity—0.0
Each score is confidence × effect size, taken from the best-evidenced benefit in that domain: the grade (A–D) sets the confidence, the measured effect sets the size. Hover a domain to see the outcomes behind it. Adverse effects are excluded and listed separately below.
OutcomeGradeEffect sizeHuman studiesWhere the evidence comes from
Growth hormone releaseCWeakModerateSmall early-phase studiesAcute, dose-dependent GH rises demonstrated in healthy volunteers in Novo Nordisk's early programme; more selective than GHRP-6, with little cortisol or prolactin rise.12
Post-operative ileus (gut recovery)CWeakNot measurable1 RCT (n=117)Median time to tolerate a solid meal 25.3 h vs 32.6 h on placebo — not statistically significant (p=0.15). No difference on secondary endpoints. Phase 3 was not pursued.3
Body compositionDNo human evidenceNot measurableNone controlledNo trial has measured muscle or fat change in people.
Sleep or recoveryDNo human evidenceNot measurableNoneUnstudied in humans.
Safety in humansadverseCWeakNot measurable1 RCT + early-phaseWell tolerated over seven days of IV dosing in the ileus trial. No long-term human safety data at the doses and durations used on the grey market.3
AMultiple good human trials, consistentBSome human trials, mostly consistentCFew or weak human studiesDAnimal or anecdotal onlyeffect size · red = adverse

Literature searched to 2 September 2026. Human studies only; animal and cell work informs the mechanism section and nothing else.

Registered trials

ClinicalTrials.gov lists 2 interventional studies naming Ipamorelin as an intervention — 2 completed, and none with results posted to the registry.

A registration is not a result. Anyone can register a study, and many never report — so this list shows what has been attempted, not what has been shown. The graded evidence above is the answer to whether something works.

StudyPhaseStatusParticipantsSponsorResults
Safety and Efficacy of Ipamorelin Compared to Placebo for the Recovery of Gastrointestinal FunctionNCT01280344 · started Apr 2011Phase 2Completed320Helsinn Therapeutics (U.S.), IncNone
Safety and Efficacy of Ipamorelin for Management of Post-Operative IleusNCT00672074 · started Apr 2008Phase 2Completed117Helsinn Therapeutics (U.S.), IncNone

Participant counts marked * are the sponsor's estimate, not a final enrolment. Source: ClinicalTrials.gov, read directly from the registry and refreshed weekly.

What it is

Ipamorelin was developed by Novo Nordisk in the 1990s as a growth-hormone secretagogue — a compound that makes the pituitary release its own growth hormone by mimicking the hunger hormone ghrelin. Its selling point in the original paper was selectivity: it raised growth hormone without the cortisol and prolactin rises seen with earlier peptides in the class.

Helsinn later licensed it and ran a phase 2 trial for post-operative ileus, the gut shutdown that follows abdominal surgery, on the theory that a ghrelin mimetic would restart motility. It did not work, and that was the end of its clinical development.

How it is thought to work

It binds the ghrelin receptor (GHS-R1a) in the pituitary and hypothalamus, triggering a pulse of growth hormone. The pulse is short-lived, which is why the grey-market practice is multiple daily injections — a regimen that has never been studied.

What is still unknown

  • Whether repeated dosing changes body composition at all; no one has measured it.
  • Long-term effects of raising growth hormone and IGF-1 in healthy adults.
  • What is in the vials sold under the name, since there is no approved manufacturer.

The molecule and how long it lasts

Identity
Formula
C38H49N9O5
Molecular weight
711.9 g/mol
CAS number
170851-70-4
PubChem
CID 9831659

PubChem record, read 23 September 2026.

Pharmacokinetics
Route
Intravenous infusion in the human study; injected subcutaneously as sold
Half-life
About 2 hours (terminal, intravenous, healthy men)

From a published human pharmacokinetic study: Gobburu JV, et al. Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharm Res 1999;16:1412–1416

Regulatory status

European Union
Unauthorised medicinal product

No marketing authorisation in any member state. Supplying it for human use is an offence under national medicines law; 'research use only' labels do not change that.

United States
Not approved; compounding barred

The advisory committee voted 0–12 against ipamorelin on 29 October 2024. Ipamorelin acetate remains in Category 2 for outsourcing facilities; its 503A nomination is listed as withdrawn (April 2026).

United Kingdom
Unlicensed medicine

Not licensed by the MHRA. Selling or supplying it is an offence under the Human Medicines Regulations 2012; importing a small quantity purely for personal use is not itself an offence, but consignments are seized.

Australia
Schedule 4, unapproved

Prescription-only substance not on the ARTG. Obtainable only on prescription (compounded or imported under the Personal Importation Scheme with a prescription). Named in the TGA's April 2026 advisory. Named in NSW law as a prescribed restricted substance.

Canada
Not authorised

No Drug Identification Number; selling it is illegal. Among the products Health Canada seized from a domestic vendor in August 2025. Residents cannot import prescription drugs by mail.

Sport (WADA)
Prohibited at all times

Growth hormone secretagogue: S2.2.4.

Questions people actually ask

Does ipamorelin build muscle?
Nobody knows. It releases growth hormone in the short term, but no trial has measured muscle or fat change in people taking it. The claim is an inference from the hormone, not a result.
Is ipamorelin safe?
It was well tolerated for a week of intravenous dosing in one trial of surgical patients. There is no human data on months of injections, which is how it is used outside medicine.
Why was ipamorelin never approved?
Its one proper randomised trial, for post-operative gut recovery, did not meet its endpoint, and the developer stopped. No company has tested it for any other indication.

One page per claimed effect

References

  1. 1
    Raun K, et al. Ipamorelin, the first selective growth hormone secretagogue.Eur J Endocrinol, 1998;139:552–561Pharmacology; animal and early human data.
  2. 2
  3. 3

Change log

  • 2026-09-02Full page. Added the negative post-operative-ileus RCT, safety row, regional status and FAQ.
  • 2026-09-01Initial publication.