A five-amino-acid ghrelin-receptor agonist that releases growth hormone. Its only efficacy trial, for post-surgery gut paralysis, failed.
Also called Ipamorelin acetate, Aib-His-D-2-Nal-D-Phe-Lys-NH2
Ipamorelin is a five-amino-acid peptide that Novo Nordisk built in the 1990s. It binds the ghrelin receptor (GHS-R1a) on the pituitary, the same receptor your stomach's hunger hormone uses, and triggers a short burst of growth hormone. Its selling point in the 1998 animal work was selectivity: in pigs it released growth hormone without the cortisol and ACTH spikes seen with older peptides like GHRP-6 and GHRP-2, even at doses 200 times higher than needed.
Two human studies exist. A 1999 dosing study in 40 healthy men gave it intravenously and found a single GH pulse peaking about 40 minutes after the dose, with a half-life of about 2 hours. A 2014 phase 2 randomized trial in 114 people after bowel surgery tested whether it would get the gut moving again sooner; it did not, with no significant difference from placebo, and development for that use ended. No human study has measured muscle, fat, sleep, recovery or skin, which are the reasons it is sold online.
Ipamorelin is not approved anywhere. An FDA advisory committee voted 12-0 (one abstention) in October 2024 against allowing pharmacies to compound it, and it remains off the 503A list. FDA flags two deaths among ipamorelin-treated patients in the bowel-surgery trial, both from surgical complications, and higher rates of low potassium and high blood sugar. WADA bans it at all times.
What it binds to, and what happens inside the body after that, step by step.
Ipamorelin binds the growth hormone secretagogue receptor (GHS-R1a), the ghrelin receptor, on pituitary somatotrophs and in the hypothalamus. That produces a single short GH pulse, which then raises IGF-1. In pigs it did not raise ACTH or cortisol, which separated it from GHRP-2 and GHRP-6; none of the three changed prolactin, FSH, LH or TSH in that study. Ghrelin receptors are also in the gut, which is why it was tested to restart bowel movement after surgery.
Human results and animal results are kept apart below. A result in rats tells you a mechanism is plausible. It does not tell you what happens in a person.
In humans, ipamorelin reliably triggers a GH pulse after an intravenous dose, and in one randomized trial it did not beat placebo for gut recovery after bowel surgery. There is no human evidence for muscle gain, fat loss, sleep, injury healing or anti-aging effects. The cortisol-sparing selectivity and bone-growth findings come from pigs and rats. The grade is B because one double-blind randomized trial exists, but that trial was negative and tested a hospital use, not the uses it is sold for.
114 adults after open or laparoscopic bowel resection, multicenter, double-blind
Median time to first tolerated solid meal was 25.3 hours with ipamorelin vs 32.6 hours with placebo, not significant (p = 0.15).
Read the study40 healthy men, 5 escalating 15-minute IV infusion doses (8 per dose)
Terminal half-life was about 2 hours; each dose produced one GH pulse peaking at 0.67 hours.
Read the studyRat pituitary cells, anesthetized rats and conscious swine
GH release matched GHRP-6, but ACTH and cortisol did not rise even at doses over 200 times the effective dose.
Read the studyRats
Repeated dosing increased longitudinal bone growth; not tested in humans.
Read the studyRats after abdominal surgery
A single IV dose shortened time to the first bowel movement, and repeated dosing raised stool output, food intake and weight gain; the effect did not carry over to the human trial.
Read the studyThese are questions the published research has not answered.
No product containing Ipamorelin is approved as a medicine by the FDA.
Clinical development for postoperative ileus ended after a negative phase 2 trial. Sold as a research chemical. Press coverage of the February 2026 HHS announcement listed ipamorelin among peptides expected to leave Category 2, but no FDA action has added it to the 503A bulks list as of this review. Prohibited at all times under WADA S2.2.4 as a growth hormone secretagogue.
How much of Ipamorelin is left after a single dose
Simple first-order model from the published half-life. Real clearance varies with dose, route, kidney and liver function and formulation. This is not a dosing schedule.
This table records the doses that trials and approved labels used, with the source for each row. It is a record of research, not a recommendation, and it is open to free members.
Which symptoms are expected and which mean stop and get help: side effects and red flags.
Tap a claim to see what the studies found.
In pigs in the 1998 study, ipamorelin did not raise ACTH or cortisol even at doses 200 times the effective dose, while GHRP-2 and GHRP-6 did. None of the three changed prolactin in pigs. Human studies did not test cortisol or prolactin, so the selectivity claim has never been confirmed in people.
No human study measured body composition. The claim is borrowed from what growth hormone does at much higher, sustained levels.
No sleep study exists. Insomnia was actually more common on ipamorelin than placebo in its one trial.
In 56 treated surgery patients, low potassium, high blood sugar and insomnia were more frequent than on placebo, and FDA cited serious adverse events in its compounding review.
Its only efficacy trial, for postoperative ileus, missed its primary endpoint, and development stopped.
These pairings come up often. Almost none have been tested together in a trial, and the evidence note on each says so plainly.
Combines a ghrelin-receptor agonist with a GHRH analog, two separate triggers for the same pituitary cells, aiming for a bigger GH pulse.
EvidenceNever studied together in humans. FDA advisory committees rejected both for compounding.
Same logic as the CJC-1295 pairing, using a shorter-acting GHRH analog.
EvidenceNo clinical trials. FDA's adverse event database contains a report of a compounded ipamorelin-sermorelin product, but no efficacy or safety study exists.
No approved product or label exists. Published stability data for research-grade powder are not available.
No validated stability data have been published. FDA notes ipamorelin may aggregate, which affects both potency and immune reactions.
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