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Ipamorelin

Ipamorelin is a synthetic pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH2) growth hormone secretagogue that activates the ghrelin/GHS-R1a receptor to trigger a short, pulse-like release of growth hormone (GH). It is not an approved drug for any indication; it never advanced past a small phase 2 trial and is sold only as an unregulated "research"/gray-market peptide. There is essentially no human evidence supporting the body-composition, recovery, or anti-aging uses for which it is marketed, and no long-term human safety data. The only controlled human safety data come from short (<=7 day) intravenous dosing in surgical patients and single-dose PK studies in healthy men; chronic self-injection is entirely uncharacterized. Because it raises GH and downstream IGF-1, the biologically plausible risks are those of GH excess: fluid retention/edema, joint and muscle pain, carpal-tunnel-type symptoms, insulin resistance/elevated blood glucose, and a theoretical (unproven) concern about promoting growth of existing tumors. Product identity, purity, and dose in gray-market vials are unverified. It is banned in sport (WADA). Anyone using or considering it should involve a physician and get bloodwork; this monograph leads with risk, not benefit.

Clinical readoutPeptide · gh-secretagogue
Hepatic strainNone
CardiovascularLow
HPTA suppressionNone
Half-life
2 h
Route
Parenteral
Evidence
C
Active
Single
2 h4 h6 h8 h10 h
Illustrative single-compartment washout · each mark = one half-life · t½ ≈ Short terminal half-life of approximately 2 hours in healthy human volunteers after IV infusion (PMID 10496658).
Pharmacology

Mechanism of action

Ipamorelin is a selective agonist of the growth hormone secretagogue receptor (GHS-R1a, the ghrelin receptor) on pituitary somatotrophs and hypothalamic neurons. Binding triggers a discrete, pulse-like release of endogenous growth hormone with potency and efficacy comparable to GHRP-6 in preclinical models, and it acts synergistically with endogenous GHRH. A defining preclinical feature is selectivity: in swine, ipamorelin released GH without significantly raising ACTH, cortisol, prolactin, FSH, LH, or TSH, even at doses >200-fold above the GH ED50 — distinguishing it from older GHRPs (GHRP-2/GHRP-6) that also raise ACTH/cortisol. Elevated GH secondarily stimulates hepatic IGF-1, the presumed mediator of anabolic/metabolic effects, though a 15-day rat study found no rise in total IGF-1. Ghrelin-receptor activation in the gut also stimulates gastric/colonic motility and appetite, which is why it was investigated for postoperative ileus.
Kinetics

Pharmacokinetics

Half-life

Short terminal half-life of approximately 2 hours in healthy human volunteers after IV infusion (PMID 10496658).

Active duration

Single, transient GH pulse: GH peaks at roughly 0.67 h and declines exponentially to negligible levels within a few hours; the GH effect is brief and does not accumulate across the tested dose range (PMID 10496658).

Route

Parenteral (intravenous in all human studies; gray-market use is subcutaneous injection). Preclinical rat data show ~20% bioavailability by the intranasal route (PMID 9879640). Not orally bioavailable as a peptide.

Metabolism & clearance

Clearance ~0.078 L/h/kg with steady-state volume of distribution ~0.22 L/kg and dose-proportional kinetics in humans (PMID 10496658). Preclinically it is comparatively resistant to metabolism and is cleared predominantly renally (excreted largely as intact peptide in urine), unlike some GHRPs cleared biliarily (PMID 9879640). Note: PK is presented for washout/monitoring context only, not for evading drug testing — ipamorelin and its metabolites are detectable by anti-doping assays.

For monitoring and washout planning, not drug-test evasion.

Reported effects

Physiological & performance effects

  • Stimulates a short, pulse-like release of endogenous growth hormone via the ghrelin/GHS-R1a receptor (human PK/PD: PMID 10496658; pharmacology: PMID 9849822)
  • Selective GH release without significant increase in cortisol, ACTH, prolactin, LH, FSH, or TSH in preclinical (swine) studies (PMID 9849822)
  • Secondarily raises IGF-1 in theory, though a 15-day rat study showed no change in total IGF-1 and no change in bone-turnover markers (PMID 10373343)
  • Stimulates gastric and colonic motility and was investigated (unsuccessfully) as a prokinetic for postoperative ileus (human RCT: PMID 25331030; rodent models: PMID 19289567, PMID 27186127)
  • Appetite stimulation via ghrelin-receptor activation (mechanistic; PMID 9849822)
  • Marketed for muscle gain, fat loss, recovery, sleep, and anti-aging, but no human trials demonstrate these outcomes — such uses are unproven and investigational (reviews: PMID 42160466, PMID 42395176)
Safety

Adverse effects by system

Cardiovascular

No specific cardiovascular toxicity signal was reported in the short-term (<=7 day) IV phase 2 trial (PMID 25331030). No dedicated human cardiovascular safety data exist. Sustained supraphysiologic GH/IGF-1 elevation is biologically associated with fluid retention and, in states of chronic GH excess, cardiac remodeling — extrapolated concern only, not demonstrated for ipamorelin (review: PMID 42395176).

Hepatic

No hepatotoxicity has been reported; as a renally cleared peptide it is not a recognized hepatotoxin, but no dedicated human hepatic-safety data exist (PMID 9879640; safety population PMID 25331030).

Endocrine / HPTA

Designed for GH selectivity: preclinically it did not significantly raise ACTH, cortisol, prolactin, or gonadotropins (PMID 9849822). However, the GH-secretagogue class in real-world self-administration has been associated with prolactin/cortisol elevations, appetite change, and dysglycemia/insulin resistance from GH-driven glucose intolerance; chronic exogenous stimulation may also blunt normal GH pulsatility (class review: PMID 42395176; reduced pituitary responsiveness in rats: PMID 10373343).

Reproductive

No direct effect on reproductive hormones was seen preclinically (no change in LH/FSH in swine; PMID 9849822). No human reproductive, fertility, or pregnancy safety data exist — use in pregnancy/lactation is uncharacterized and should be avoided.

Neuropsychiatric

No established psychiatric adverse effects and no human data. Ghrelin-receptor involvement in appetite/reward makes effects theoretically possible but unstudied (no adequate human data; PMID 42395176).

Renal

Renally excreted; no nephrotoxicity reported. GH-mediated sodium/fluid retention (edema) is a plausible class effect but not directly demonstrated for ipamorelin in humans (review: PMID 42395176).

Hematologic

No known hematologic effects and no adequate human data (PMID 25331030).

Dermatologic

Injection-site reactions are reported for injectable GH-axis peptides used off-label; sterility/purity of gray-market product is a compounding concern (review: PMID 42395176; product-quality concerns: PMID 42160466). No other dermatologic effects established.

Recovery

HPTA suppression & recovery

Suppression: Not a suppressor of the hypothalamic-pituitary-gonadal (HPTA) axis; primary endocrine concern is the GH-IGF-1 axis and glucose metabolism, not testosterone.

Ipamorelin is not androgenic and does not act on the gonadal axis, so classic post-cycle testosterone recovery and SERM therapy are not applicable; a SERM should not be used to 'recover' from ipamorelin. The relevant concern is the GH-IGF-1 axis: chronic exogenous GH-secretagogue stimulation may transiently blunt endogenous GH regulation (reduced pituitary responsiveness seen in rats; PMID 10373343), and GH excess can impair glucose tolerance (class review: PMID 42395176). Any perceived hormonal disturbance, abnormal IGF-1/glucose labs, or GH-axis question should be evaluated and managed by an endocrinologist rather than self-treated.

Bloodwork & vitals

Monitoring

Recommended labs & checks
IGF-1Fasting glucose and HbA1cProlactin and morning cortisolComprehensive metabolic panel (including electrolytes and liver enzymes)CBCThyroid panel (TSH, free T4)

Cadence: Baseline before any use, then periodic (e.g., every 3 months) if used at all, and promptly if new symptoms arise; all monitoring should be overseen by a physician/endocrinologist.

Warning signs — seek care
  • Peripheral edema or rapid weight gain (fluid retention)
  • New or worsening joint/muscle pain or carpal-tunnel-type numbness/tingling
  • Rising fasting glucose/HbA1c or symptoms of hyperglycemia
  • Palpitations or shortness of breath
  • Persistent nausea or vomiting
  • Injection-site redness, swelling, pain, or signs of infection
  • Headache or visual changes
Do not use if

Contraindications

  • Active or prior malignancy, or high cancer risk — GH/IGF-1 elevation is mitogenic and could theoretically promote tumor growth (biologically plausible, unproven; PMID 42395176)
  • Diabetes, impaired glucose tolerance, or insulin resistance — GH excess worsens glycemic control (PMID 42395176)
  • Pregnancy and breastfeeding — no safety data (no adequate human data)
  • Known hypersensitivity to the peptide or vial excipients
  • Use as an unapproved performance/physique/anti-aging agent generally — no regulatory approval and no human efficacy evidence for these uses (PMID 42160466, PMID 42395176)
  • Competitive athletes — prohibited by WADA/anti-doping regulations (PMID 42160466)
Combinations

Interaction profile

  • MajorWith insulin: Metabolic / glucose
  • ModerateWith another GH secretagogue: Metabolic / glucose
  • ModerateWith growth hormone: Metabolic / glucose
  • ModerateWith IGF-1: Metabolic / glucose
  • ModerateWith a GLP-1 / incretin agonist: Metabolic / glucose
  • ContraindicatedWith DNP: Additive cardiovascular strain

Check a specific combination in the interaction checker.

Harm reduction

Reducing harm & when to stop

  • There is no human evidence that ipamorelin improves muscle, fat loss, recovery, or aging outcomes, and no long-term human safety data — understand you are self-experimenting with an unapproved compound.
  • Do not use without physician involvement; get baseline bloodwork (IGF-1, fasting glucose/HbA1c, prolactin, cortisol, metabolic panel) and repeat periodically.
  • Avoid entirely if you have any history of cancer, diabetes/impaired glucose tolerance, or are pregnant or breastfeeding.
  • Stop and seek medical care for: significant swelling/rapid weight gain, new joint pain or hand numbness/tingling, rising blood sugar, palpitations or breathlessness, persistent vomiting, or signs of injection-site infection.
  • Gray-market vials have unverified identity, dose, purity, and sterility; contamination and mislabeling are real risks and cannot be dosed around safely.
  • This is not a substitute for evaluation of low GH/IGF-1 by an endocrinologist; genuine GH deficiency has approved, monitored therapies.
  • Prohibited in competitive sport (WADA) and detectable on anti-doping assays.
  • Do not use a SERM to 'recover' from ipamorelin — it does not act on the testosterone axis; any hormonal or metabolic concern should go to an endocrinologist.
Evidence

Citations (10)

Every clinical claim above is tied to a primary source. Overall evidence grade C — graded to the best available evidence for its core claims.

  1. 01

    Ipamorelin is a synthetic pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH2) that acts as a GHS-R1a/ghrelin-receptor agonist and releases GH with potency/efficacy comparable to GHRP-6.

    PreclinicalIpamorelin, the first selective growth hormone secretagogue.PMID 9849822 ↗

  2. 02

    Ipamorelin is selective for GH release, not significantly raising ACTH, cortisol, prolactin, FSH, LH, or TSH in swine even at doses >200-fold above the GH ED50.

    PreclinicalIpamorelin, the first selective growth hormone secretagogue.PMID 9849822 ↗

  3. 03

    In healthy human volunteers, IV ipamorelin has a terminal half-life of ~2 h, clearance ~0.078 L/h/kg, Vss ~0.22 L/kg, dose-proportional PK, and produces a single GH pulse peaking near 0.67 h that declines to negligible levels.

    RCTPMID 10496658 ↗

  4. 04

    Ipamorelin is comparatively metabolically stable, cleared predominantly renally with substantial intact-peptide urinary excretion, and shows ~20% intranasal bioavailability in rats.

    PreclinicalPMID 9879640 ↗

  5. 05

    In a phase 2 double-blind placebo-controlled RCT, ipamorelin 0.03 mg/kg IV twice daily for up to 7 days in bowel-resection patients was well tolerated but did not significantly improve time to first tolerated meal versus placebo (25.3 vs 32.6 h, p=0.15); treatment-emergent adverse events occurred in 87.5% (ipamorelin) vs 94.8% (placebo), including nausea and vomiting.

    RCTPMID 25331030 ↗

  6. 06

    Ipamorelin accelerates gastric emptying and gastrointestinal transit via ghrelin-receptor-mediated stimulation of gut motility in rodent postoperative-ileus models.

    PreclinicalPMID 19289567 ↗

  7. 07

    Ipamorelin reverses surgery-induced suppression of gastric smooth-muscle contractility through a ghrelin-receptor mechanism in a rodent postoperative-ileus model.

    PreclinicalPMID 27186127 ↗

  8. 08

    A 15-day course of ipamorelin increased longitudinal bone growth and body weight in rats without changing total IGF-1 or bone-turnover markers, and marginally reduced subsequent pituitary GH responsiveness.

    PreclinicalPMID 10373343 ↗

  9. 09

    Growth-hormone-secretagogue peptides including ipamorelin remain investigational with uncertain safety, no regulatory approval for performance/physique uses, product-quality concerns, and reported adverse effects including prolactin/cortisol elevation, dysglycemia, fluid retention, myalgia/arthralgia, and injection-site reactions.

    ReviewThe emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration.PMID 42395176 ↗

  10. 10

    Injectable GH-axis secretagogues (CJC-1295, ipamorelin, tesamorelin) remain experimental with uncertain safety and product-quality concerns and are subject to anti-doping restrictions; overall evidence is predominantly low (Level V / grade C).

    ReviewPMID 42160466 ↗

Last reviewed 2026-07-06 · Verified against PubMed · Educational, not medical advice