Ipamorelin human trials: the complete published record

Published August 28, 2026 · Artemis Labs

Ipamorelin has been studied in humans twice in the published literature. A 1999 study in healthy male volunteers measured how the peptide cleared from the body and how growth hormone responded, reporting a terminal half-life of about two hours. A 2014 multicenter, double-blind, placebo-controlled phase 2 trial tested whether it helped 114 patients recover bowel function after surgery, and it did not: median time to a tolerated meal was 25.3 hours with ipamorelin against 32.6 with placebo, a difference that did not reach statistical significance. The authors concluded there were “no significant differences between ipamorelin and placebo in the key and secondary efficacy analyses.” No later ipamorelin efficacy trial appears in the PubMed record.

Key findings

• Two human studies, total. Both are indexed with clinical-trial publication types: PMID 10496658 (1999) and PMID 25331030 (2014).
• The 2014 trial was properly built for the question — “multicenter, double-blind, placebo-controlled” — and registered as NCT00672074.
• Its result was null on the primary endpoint: 25.3 hours versus 32.6 hours, p = 0.15.
• Safety in that trial was unremarkable: treatment-emergent adverse events occurred in 87.5% of the ipamorelin group and 94.8% of the placebo group — a reminder that the placebo arm of surgical recovery is not a quiet baseline.

The 1999 pharmacokinetic study

The first human work was not about whether ipamorelin helps anyone. It was about what the body does with the molecule. Healthy male volunteers received one of five ascending infusion rates over fifteen minutes, with eight subjects at each level, and researchers measured both ipamorelin and growth hormone concentrations over time.

Three numbers came out of it. The terminal half-life was about two hours. Clearance was 0.078 litres per hour per kilogram. The volume of distribution at steady state was 0.22 litres per kilogram. Growth hormone rose to a peak at about 0.67 hours and then declined to negligible concentrations at every dose.

The authors also noted something that later work echoes: “The inter-individual variability of the PD parameters was larger than that of the PK parameters.” In plain terms, the body handled the peptide fairly consistently from person to person; the hormone response to it varied much more.

This study is the source of the “about two hours” half-life figure that circulates widely. It is a real, human, published number, and it is worth knowing that it comes from eight-subject dose groups in a 1999 pharmacokinetic model — not from a large clinical program.

The 2014 trial, and why it is the important one

Postoperative ileus is the period after abdominal surgery when the bowel is slow to restart. It is a real clinical problem with, as the trial’s own background section puts it, few effective management strategies. Because the ghrelin receptor is present in the gut and ghrelin-receptor agonists speed gastric emptying in animals, ipamorelin was a reasonable candidate — and the rodent work described on our gut motility page supported the idea.

The trial was designed to answer the question properly. It was multicenter. It was double-blind. It had a placebo arm. It enrolled adults having small and large bowel resection by open or laparoscopic surgery, and it pre-specified its endpoint: time from the first dose to tolerating a standardized solid meal. One hundred and seventeen patients were enrolled and 114 formed the safety and modified intent-to-treat populations.

The ipamorelin group tolerated a meal at a median of 25.3 hours. The placebo group did so at 32.6 hours. Seven hours sounds like something. But the difference carried a p value of 0.15, meaning a gap that size could easily have arisen by chance in a study this size — and the authors did not dress it up. Their conclusion states plainly that ipamorelin “was well tolerated” and that there were “no significant differences between ipamorelin and placebo in the key and secondary efficacy analyses.”

They also named the study’s own weakness: “This proof of concept study was small and enrolled patients with a broad range of underlying conditions.” A well-run negative trial with its limitations stated is a good piece of science. It is also the whole of ipamorelin’s human efficacy record.

What the research does not show

No published human trial shows ipamorelin producing a clinical benefit. The only adequately designed test of a clinical outcome returned a null result.

There is no published human research on ipamorelin for body composition, athletic performance, recovery from injury, sleep, or ageing. Those uses are discussed in review articles about what people are doing, not in trials of whether it works. Recent reviews are direct about this: a 2026 structured review classes growth hormone axis secretagogues including ipamorelin as remaining “investigational, with uncertain safety profiles, product quality concerns, and widespread antidoping restrictions” (PMID 42160466).

There is no long-term human exposure data at all. The longest human dosing period in the record is the 2014 trial’s seven days or discharge, whichever came first.

And a point about the shape of the evidence rather than its content: the 1999 study measured a hormone rising, which is a biomarker. The 2014 study measured whether patients ate sooner, which is an outcome. The first succeeded and the second did not, and that gap between “the biology moved” and “it helped” is the single most useful thing to carry away from this record.

Frequently asked questions

Is ipamorelin FDA-approved?

No. Review literature published in 2026 lists it among unapproved peptides (PMID 41966639), and the trial record above is the extent of its published clinical testing.

Did the 2014 trial find safety problems?

It reported the compound was well tolerated. Adverse events were common in both arms, slightly more so in the placebo arm, which is typical for patients recovering from bowel surgery.

Why did development stop?

We do not publish a reason, because no primary source we retrieved states one. What the record shows is that no later efficacy trial of ipamorelin appears in PubMed.

What does the animal research show that the human research does not?

Growth hormone release, bone growth, gut transit and appetite effects — all in rats, mice, ferrets, swine and fish. Those results are covered on our pages on bone and muscle and what ipamorelin is studied for.

References

1. Gobburu JV, Agersø H, Jusko WJ, Ynddal L. Pharm Res. 1999. PMID 10496658. DOI 10.1023/a:1018955126402.
2. Beck DE, Sweeney WB, McCarter MD. Int J Colorectal Dis. 2014. PMID 25331030. DOI 10.1007/s00384-014-2030-8.
3. Villegas Meza AD, et al. JBJS Rev. 2026. PMID 42160466.
4. Mendias CL, Awan TM. Sports Med. 2026. PMID 41966639.

Methodology: the human record was established by retrieving every PubMed entry for ipamorelin on August 28, 2026 and filtering on clinical-trial publication types. Quoted results are verbatim from the published abstracts.

All compounds sold by Artemis Labs are for laboratory research use only. Nothing on this page is medical advice, and no statement has been evaluated by the FDA.