# Ipamorelin: Selectivity, Side Effects, and the Limits of the Evidence

> Ipamorelin is a selective growth-hormone secretagogue. The safety record first: reported side effects, water retention, the one failed human trial, and the long-term data gap. Cited.

A selective ghrelin-receptor peptide. One failed human trial, a two-hour half-life, no long-term safety data. Every figure cited.

## The short version

Ipamorelin is a small lab-made peptide (a short chain of amino acids — the building blocks of proteins). It tells the pituitary gland to release a pulse of growth hormone. Its one defining trait: it does this cleanly. It barely touches cortisol (the stress hormone) or prolactin, where older peptides did. That selectivity is the headline.

The safety record is thin, and that matters more than the upside. Ipamorelin has never been approved as a drug, anywhere. Its only published human trial — for slow bowel recovery after surgery — failed to beat placebo [3]. No long-term human safety study exists. People report side effects: a warm facial flush after injecting, mild puffiness, more hunger, occasional dizziness. Those are community reports, not trial data. What people report — including the downsides — and the cited cautions are on [the effects page](/effects).

## What the literature establishes

Ipamorelin (sequence Aib-His-D-2-Nal-D-Phe-Lys-NH2) is a synthetic pentapeptide — five linked amino acids. It activates the ghrelin receptor (GHS-R1a, the docking site on cells that the natural "hunger hormone" ghrelin uses), which triggers growth-hormone release from the pituitary. In its founding 1998 characterization it released GH potently in rat pituitary cells, rats, and swine (swine ED50 = 2.3 nmol/kg vs 3.9 nmol/kg for GHRP-6), yet did not raise ACTH or cortisol above baseline even at doses more than 200-fold above its GH ED50 [1]. That is the selectivity finding. It is the reason ipamorelin exists as a distinct compound and not just another growth-hormone-releasing peptide.

The quantitative anchors are few and precise. Terminal half-life in healthy human volunteers: approximately 2 hours, IV [2]. GH response: a single discrete pulse peaking near 40 minutes after dosing [2]. In adult female rats, subcutaneous ipamorelin raised longitudinal bone-growth rate dose-dependently from 42 to 52 μm/day over 15 days — with no measured change in total IGF-1 (a hormone that carries many of GH's downstream effects) [4]. The most recent in-vivo study, a 2024 ferret model, found that ipamorelin (1-3 mg/kg) cut chemotherapy-induced weight loss by roughly 24% but had no anti-nausea effect [5].

## Where the data runs out

Human evidence is limited and largely negative. The only published Phase 2 randomized trial (NCT00672074; 114 adults, 0.03 mg/kg IV twice daily for up to 7 days) missed its primary endpoint: median time to first tolerated meal was 25.3 h with ipamorelin vs 32.6 h with placebo (p=0.15) [3]. No Phase 3 trial was run. No indication was approved.

Long-term safety is uncharacterized. There is no chronic human safety database. A 28-day study of a different ghrelin-receptor agonist (GSK894281) found dose-dependent heart-muscle degeneration in rats — a class-level signal, not an ipamorelin finding, but the reason chronic systemic dosing in this receptor class warrants scrutiny [6]. The popular CJC-1295 + ipamorelin pairing rests on the separate pharmacology of each agent, not on any trial of the combination. This site indexes the [Ipamorelin research](/research) and reads it straight: confirmed where confirmed, blank where blank.

## What this site is

A monochrome digest of the published ipamorelin record. Not a clinic. Not a prescriber. No medical advice, no dosing for people, nothing for sale. The word "clinic" in the domain is editorial framing — the stance of a publisher reading the clinical literature, not a service. The pages: [Ipamorelin effects](/effects) for what people report and what the cautions say, [Ipamorelin research](/research) for the mechanism and the studies, dosing in research context, the questions readers actually ask, and the full [Ipamorelin references](/references) with PMIDs and DOIs. Two dedicated reads — water retention, and how long it stays in your system — sit alongside.

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A safety-led readout of the ipamorelin record — the reported side effects, the water-retention question, and the lone failed human trial logged first, with the long-term-safety line left openly blank; no clinic behind the console and nothing here dosed, prescribed, or sold.