PK CONSOLE / IPAMORELIN — t1/2 ~2 H
Ipamorelin clears in about two hours and fires a single growth-hormone pulse near the 40-minute mark.
A pharmacokinetics-first digest of the published ipamorelin literature — half-life, clearance, the GH-selectivity that defines it, and the one human trial that read out — with every number cited.
Start here
Ipamorelin is a small, lab-made peptide (a short chain of building blocks called amino acids) that tells the pituitary gland — a hormone control hub at the base of the brain — to release a quick burst of growth hormone (GH), the body's main signal for tissue growth and repair. This site reads ipamorelin through its pharmacokinetics: the simple question of how fast it goes up and how fast it comes back down. The short answer is that it acts fast and leaves fast. In healthy adults given it by vein, the level falls by half about every two hours, and the growth-hormone burst it triggers peaks around 40 minutes, then fades [1]. What people use it for, what the research has and hasn't shown, and what to watch for — including the downsides — is on the effects page. One honesty note up front: the only completed human trial of ipamorelin did not work for the condition it was tested on [2]. And despite the word in this domain, this is a research digest — it is not a pharmacy, it stocks nothing, and ipamorelin is not an approved medicine.
What the pharmacokinetics actually show
The clearest human ipamorelin data come from a pharmacokinetic-pharmacodynamic (PK/PD — how the drug moves through the body and what effect that movement produces) study in healthy male volunteers. Across five intravenous doses from 4.21 to 140.45 nmol/kg, the kinetics were dose-proportional: terminal half-life about 2 hours, clearance 0.078 L/h/kg, and steady-state volume of distribution 0.22 L/kg [1]. The growth-hormone response read out as one discrete pulse peaking near 0.67 hours — roughly 40 minutes — after dosing [1]. That tidy profile is the spine of this digest. A short half-life means ipamorelin is gone from the bloodstream long before its downstream effect has fully played out, which is why timing-of-dose questions matter more than steady-level ones. The numbers above, and the time-course they describe, are detailed on the how long does ipamorelin stay in your system page.
Selectivity is the trait that named it
Ipamorelin (sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2) was the first growth hormone secretagogue characterized as highly selective — meaning it raises GH while leaving other stress hormones largely untouched. In its founding study it released GH potently in rat pituitary cells, anaesthetized rats, and conscious swine (swine ED50 = 2.3 nmol/kg versus 3.9 nmol/kg for GHRP-6), yet did not raise ACTH or cortisol above the level seen with GHRH even at doses more than 200-fold above its GH ED50 [3]. It works through the ghrelin receptor — formally GHS-R1a, the same receptor the hunger hormone ghrelin uses — on the pituitary's GH-producing cells [3]. That receptor choice is also why appetite shows up later as a reported effect. The selectivity is real and well-documented; it is the single most reproducible thing in the ipamorelin record.
Where the human evidence stands
Human evidence is thin and, for the indication tested, negative. The only published Phase 2 randomized controlled trial gave ipamorelin to 114 adults after bowel-resection surgery (0.03 mg/kg IV twice daily for up to 7 days) to treat postoperative ileus — the temporary bowel-motility stall that follows abdominal surgery. It missed its primary endpoint: median time to first tolerated meal was 25.3 hours with ipamorelin versus 32.6 hours with placebo (p=0.15) [2]. No ipamorelin-specific safety signal emerged in that short window, but efficacy was not shown, and no further clinical development followed [2]. Preclinically the picture is more active: in adult female rats, 15 days of subcutaneous ipamorelin raised the longitudinal bone-growth rate dose-dependently, from 42 to 52 microns/day at the highest dose — without measurable change in systemic IGF-1 [4]. The most recent in-vivo study, in ferrets in 2024, found ipamorelin reduced chemotherapy-driven weight loss by about 24% through a peripheral mechanism, with no anti-emetic effect [5]. Dig into the mechanism and the studies on the Ipamorelin research page, and see the full source list on the Ipamorelin references page.
Status, in one line
Ipamorelin has never been approved as a drug by any regulator [2]. It is banned in sport at all times as a growth hormone secretagogue (WADA category S2), and in 2024 the FDA removed ipamorelin acetate from Category 2 of the interim Section 503A bulk-substances list and reviewed it at an October 2024 advisory-committee meeting, restricting compounding-pharmacy access. Most use is off-label and self-administered, outside any controlled-trial support [2]. This digest documents that record; it does not sell, supply, or recommend anything.