# Ipamorelin: The Safety Record, Half-Life Data, and the One Human Trial > Ipamorelin, lead-first from the safety lens: one failed Phase 2 trial, a ~2 h human half-life, a class cardiotoxicity signal, and the long-term unknowns — every figure cited. The tolerability record read first — reported side effects, the pharmacokinetics, and the open questions, with every quantitative claim pinned to the study that measured it. ## Start here Ipamorelin is a lab-made peptide (a short chain of five building blocks called amino acids) that tells the pituitary gland — a pea-sized gland under the brain — to release a pulse of growth hormone. Its claim to fame is being clean: it raises growth hormone without raising the stress hormone cortisol [1]. People in research-use communities try it for deeper sleep, faster recovery, and a slowly leaner body. Here is the honest state of the evidence: the one real human trial, in surgery patients, did not work — it missed its goal [3]. In people, the drug leaves the blood fast, with a half-life of about two hours [2]. And no long-term human safety study exists in anyone. This site reads that record from the safety side first. What people report — including the downsides — is on [the effects page](/effects), and the time-in-body numbers are on the [half-life page](/half-life). Nothing here is a dose, a prescription, or medical advice. ## The safety record in one screen Start with the numbers that matter for tolerability. **Ipamorelin** has exactly one published human efficacy trial, and it failed. In 114 adults recovering from bowel surgery, 0.03 mg/kg given by vein twice daily moved the median time to a first tolerated meal to 25.3 hours, versus 32.6 hours on placebo — a difference that was not statistically significant (p=0.15) [3]. The flip side: in that short perioperative window, treatment-emergent adverse events occurred in 87.5% of the ipamorelin arm and 94.8% of the placebo arm, so the drug did not add a safety signal over surgery itself [3]. In healthy volunteers, ipamorelin clears quickly — a terminal half-life of roughly 2 hours by vein, with the growth-hormone response arriving as a single pulse about 40 minutes after dosing [2]. That short residence is the reproducible PK fact this site keeps returning to. What is missing is the long view. No Phase 3 trial has been run, and no long-term human safety database exists [3]. A 28-day study of a *different* growth-hormone-secretagogue-receptor agonist (same receptor class, not ipamorelin itself) found dose-dependent heart-muscle damage in rats [6] — a class-level signal that is the reason "we don't know the chronic risk" is the correct sentence here, not a reassurance. ## What ipamorelin is, in plain terms Ipamorelin (sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2; also coded NNC 26-0161) is a synthetic pentapeptide — five amino acids, wholly man-made, not a hormone your body produces. It works by switching on the ghrelin receptor (GHS-R1a), the same receptor the natural "hunger hormone" ghrelin uses, on the growth-hormone-producing cells of the pituitary [1]. Flipping that switch triggers a discrete pulse of growth hormone (GH). Its defining trait is **selectivity**. In its founding 1998 characterization, ipamorelin released GH as potently as the older peptide GHRP-6 (swine ED50 2.3 nmol/kg vs 3.9 nmol/kg) yet did not raise ACTH or cortisol above the level seen with GHRH — even at doses more than 200-fold above its GH-releasing threshold [1]. That cortisol-and-prolactin-sparing profile is what separated it from earlier growth-hormone-releasing peptides. A naming note that matters for safety: this site is about **pure ipamorelin**, not the popular CJC-1295 + ipamorelin combination. The two are different molecules studied differently; where the combination has data, this site labels it as such on the [Ipamorelin research](/research) page. ## "Prescribed" is the wrong word — here is why that matters The domain says "prescribed," and the honest correction belongs up front: **ipamorelin is not a prescribable, approved drug.** It has never been approved by the FDA, the EMA, or any regulatory authority, for any indication [3]. The only indication that ever reached Phase 2 — postoperative ileus — failed its primary endpoint, and no further clinical development followed [3]. In 2024 the FDA removed ipamorelin acetate from Category 2 of the interim Section 503A bulk-substances list and reviewed it at the October 29, 2024 Pharmacy Compounding Advisory Committee meeting, tightening compounding-pharmacy access rather than opening it. So "prescribed ipamorelin" describes a thing that, strictly, does not exist as an approved prescription product. What exists is research-grade material and a literature — most of it preclinical, some of it human PK, one failed human trial — and that literature is what this site documents. Recent narrative reviews reach the same conclusion: a 2026 gerontology review groups ipamorelin with non-approved peptides lacking long-term safety data [17], and a 2026 orthopaedic review calls for rigorous clinical evaluation before any adoption [16]. ## How to read this site The pages are ordered the way a careful reader would want them. [Ipamorelin effects](/effects) leads with what people actually report — benefits and downsides, clearly labeled as anecdote — then the cited safety cautions. [Ipamorelin research](/research) covers the mechanism, the human PK trial, the failed efficacy trial, and the CJC-1295 / sermorelin / tesamorelin comparisons. The dosing page describes only what was administered to which species at which dose — never a human recommendation. Two focused pages answer the questions people search most from the safety angle: [does ipamorelin cause water retention](/water-retention) and [how long does ipamorelin stay in your system](/half-life). Every figure on every page traces back to a numbered source in the [Ipamorelin references](/references). --- A tolerability-first read of the ipamorelin record — the failed Phase 2 endpoint, the two-hour half-life, and the class cardiotoxicity signal logged before anything flattering, every figure carried back to the study that measured it; a reference console, never a clinic, a prescriber, or a store.