Ipamorelin
Ipamorelin
Selective GHRP secretagogue releasing growth hormone with relatively minimal cortisol/prolactin effect.
Key takeaways
- Most selective GHRP — raises GH with minimal cortisol, prolactin, or appetite effects.
- Short half-life (~2 hours) drives one to three daily subcutaneous doses in research protocols.
- Reached phase 2 human trials (postoperative ileus, negative); never approved anywhere.
- Often paired with a GHRH analog like CJC-1295 without DAC for synergistic GH pulses.
Overview
What it is
Ipamorelin is a pentapeptide growth hormone secretagogue that acts on the ghrelin (GHS-R1a) receptor to trigger pulsatile GH release from the pituitary. It's the most selective of the GHRP class, with minimal effect on cortisol, prolactin, and appetite compared with GHRP-2 or GHRP-6.
Pharmacokinetics
Estimated half-life is roughly two hours with around 60% subcutaneous bioavailability, so research protocols dose it one to three times daily. It's often paired with a GHRH analog like CJC-1295 without DAC, since the two pathways amplify each other.
What the evidence says
Ipamorelin reached early human trials, including a phase 2 study in postoperative ileus that missed its endpoint, and development stopped there. It's approved nowhere, and long-term safety data for chronic GH elevation is thin.
Reported dosing protocols
Protocols reported in research literature and clinic/community use — informational context, not a dosing recommendation.
| Use case | Dose | Route | Frequency | Duration |
|---|---|---|---|---|
| GH support (community) | 100–300 mcg | SubQ | 1–3× daily | 8–12 weeks |
Pharmacokinetic summary
- Model tier
- Simple (t½ + F, Tmax estimated)
- Half-life
- 1.9 hours
- Bioavailability
- 60%
- Typical dose
- 0.1–0.5 mg
Frequently asked questions
How is ipamorelin different from other GHRPs?
Selectivity. GHRP-6 spikes hunger, and GHRP-2 raises cortisol and prolactin at higher doses. Ipamorelin triggers a comparable GH pulse with minimal effect on those axes, which is why it became the default GHRP in clinic and community protocols.
Why take ipamorelin multiple times per day?
Its half-life is only about two hours, and the goal is amplifying natural GH pulses rather than sustained elevation. Doses are typically spread across the day, with one before bed to match the nocturnal GH surge.
Is ipamorelin approved or legal?
It isn't approved by the FDA or any major regulator; development stopped after a negative phase 2 trial in postoperative ileus. In most countries it's sold as a research chemical, and WADA prohibits it for tested athletes under S2.
References
- PubMed (Ipamorelin PK) — GHRP-1 derivative; ~2 hour half-life, comparatively clean side-effect profile.
- Raun et al., Eur J Endocrinol 1998 — ipamorelin, the first selective GH secretagogue — Human pharmacology study establishing selectivity for GH over cortisol and prolactin.
Related compounds
GHRP-2
Growth hormone secretagogue that acts on the ghrelin receptor to amplify GH pulses.
GHRP-6
Ghrelin-receptor secretagogue that increases GH and notably stimulates appetite.
MK-677 (Ibutamoren)
Orally active growth hormone secretagogue (ghrelin receptor agonist) that elevates GH and IGF-1; the non-peptide counterpart to injectable GHRPs.
Protocols featuring Ipamorelin
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