A five-amino-acid peptide that triggers a short burst of growth hormone through the ghrelin receptor without raising cortisol or prolactin. A drug company tested it between 2008 and 2013 for sluggish bowels after surgery and stopped, and it is now sold without approval for muscle, recovery, and anti-aging claims that no trial supports.
Ipamorelin is a synthetic five-amino-acid peptide that acts on the growth hormone secretagogue receptor, the same receptor the stomach hormone ghrelin uses. Binding there makes pituitary cells release a single pulse of growth hormone, which peaks within the first hour after a dose and fades within hours. What set it apart from earlier growth hormone-releasing peptides is selectivity, since in pigs it did not raise ACTH or cortisol even at doses far above those needed for growth hormone release, and it left FSH, LH, prolactin, and TSH unchanged. That cleaner profile is why it was picked for drug development.
Into a skin fold (1/7)
Ipamorelin, a peptide of 5 amino acids, is injected into a pinch of skin.
In healthy men it had a terminal half-life of about 2 hours and dose-proportional blood levels, and growth hormone output rose with dose up to a ceiling. Because it mimics ghrelin, it also stimulates the gut, which is why it was tested for postoperative ileus, the temporary paralysis of the bowel after surgery. Raising growth hormone in a pulse does not by itself prove any effect on muscle, fat, or aging. The hormone changes are measurable, while the downstream benefits claimed for it are not.
Ipamorelin is sold online and by some compounders for muscle gain, fat loss, sleep, recovery, and anti-aging. In human research it has been studied for only two things: how it raises growth hormone in healthy volunteers, and whether it speeds the return of bowel function after abdominal surgery. In the surgery trial of 117 patients it did not beat placebo, and a larger follow-up trial of 320 patients was completed in 2013 without a published result. No study has tested the uses it is marketed for.
In the trials it was given as an intravenous infusion in hospital, twice daily for up to 7 days, at 0.03 mg per kilogram. Products sold today are injected under the skin by users at home, a route and setting the trials never tested. The FDA notes that ipamorelin acetate contains unnatural amino acids that complicate quality control, and that a published study reported serious adverse events including death when it was given intravenously for gastric motility. Development stopped after the second surgery trial, and no approval followed.
Human data come from a dose-escalation study in healthy men, eight at each of five infusion rates, and two phase 2 trials in surgical patients. The 117-patient proof-of-concept trial found a median time to a first tolerated meal of 25.3 hours with ipamorelin and 32.6 hours with placebo, a difference that was not statistically significant. The 320-patient follow-up trial finished in 2013 and has no published results. Animal work established its selectivity for growth hormone release.
No trial has ever tested ipamorelin for muscle, body composition, recovery, sleep, or aging. Whether repeated growth hormone pulses over months benefit or harm healthy adults is unknown, and the products sold online have not been shown to match the material used in trials. The FDA placed ipamorelin acetate in the category of substances that raise significant safety risks for compounding in 2023. Its abandoned drug development is part of the evidence record.
In the postoperative trial, adverse events were common in both groups, 87.5% with ipamorelin and 94.8% with placebo, with no safety signal that separated them. The FDA's compounding review cites a published report of serious adverse events including death when ipamorelin was given intravenously for gastric motility, and it flags immunogenicity from aggregation and impurities as risks of compounded versions. The volunteer studies found a short-lived growth hormone pulse and little else. Long-term effects of repeated use at home are unknown.
No regulator has approved this compound, and no company is seeking approval.
Ipamorelin is not approved by the FDA or any other regulator. The FDA lists compounded drugs containing ipamorelin acetate among bulk substances that may present significant safety risks, citing immunogenicity, aggregation, peptide impurities, and a published report of serious adverse events including death with intravenous use. The World Anti-Doping Agency prohibits growth hormone secretagogues including ipamorelin. Health Canada names it among unauthorized injectable peptide drugs it has seized.