Ipamorelin

Ipamorelin (Aib-His-D-2-Nal-D-Phe-Lys-NH2; MW 711.87 Da) is a synthetic pentapeptide that acts as a selective agonist of the ghrelin receptor, also designated the growth hormone secretagogue receptor type 1a (GHS-R1a). Developed by Novo Nordisk and first characterized by Raun et al. in 1998, it was described as the first selective growth hormone secretagogue.

GHS-R1a activation at anterior pituitary somatotroph cells increases intracellular calcium through the phospholipase C/IP3 pathway and suppresses hypothalamic somatostatin release, together amplifying episodic GH secretion. In rat pituitary cell assays, ipamorelin achieved an EC50 of approximately 1.3 nmol/L with 85% maximal GH efficacy relative to a reference stimulus. In conscious swine, the in vivo ED50 was 2.3 nmol/kg, yielding peak plasma GH of 65 ng/mL, comparable to GHRP-6 in that model.

The defining characteristic is endocrine selectivity. Unlike GHRP-2, GHRP-6, and hexarelin, ipamorelin did not elevate ACTH or cortisol at doses more than 200-fold above its GH ED50, and did not affect prolactin, FSH, LH, or TSH. GHS-R1a stimulation preserves the natural pulsatile pattern of GH release and permits normal feedback inhibition by IGF-1 and somatostatin, a key distinction from exogenous GH administration. Human pharmacokinetic studies confirmed a terminal plasma half-life of approximately 2 hours.

The primary human pharmacokinetic/pharmacodynamic study (Gobburu et al. 1999, PMID 10496658) administered ipamorelin intravenously to 40 healthy male volunteers at five escalating doses (4.21 to 140.45 nmol/kg over 15 minutes). Kinetics were dose-proportional; the terminal half-life was 2 hours, clearance 0.078 L/h/kg, and volume of distribution at steady-state 0.22 L/kg. Peak GH occurred at 0.67 hours post-infusion and returned to baseline within approximately 6 hours. The concentration producing half-maximal GH stimulation (SC50) was 214 nmol/L, with a maximal GH production rate of 694 mIU/L/h.

The only controlled efficacy trial in humans is a Phase 2, double-blind, placebo-controlled multicenter study (Beck et al. 2014, PMID 25331030; NCT00672074) enrolling 117 patients undergoing bowel resection. Ipamorelin 0.03 mg/kg IV twice daily was given for up to 7 days. The primary endpoint, median time to tolerance of a standardized solid meal, was 25.3 hours with ipamorelin versus 32.6 hours with placebo (p = 0.15); the difference was not statistically significant. Treatment-emergent adverse events occurred in 87.5% of the ipamorelin group and 94.8% of placebo. The drug was described as well tolerated, but Helsinn Therapeutics discontinued development.

In animal research, ipamorelin induced dose-dependent longitudinal bone growth in rats at doses of 40 to 1000 mcg/kg per day without altering IGF-1 or bone-turnover markers (Johansen et al. 1999, PMID 10373343). A 12-week subcutaneous infusion study in adult female rats showed that ipamorelin increased total bone mineral content by expanding cross-sectional bone area, without changing volumetric bone density (Svensson et al. 2000, PMID 10828840). No published randomized trial has examined ipamorelin's effect on body composition, physical performance, or anti-aging outcomes in humans.

Typical dosage: 200-300 mcg (twice-daily).

The only published human dosing data come from clinical research settings. The Phase 2 post-operative ileus trial (Beck et al. 2014) used 0.03 mg/kg intravenously twice daily for up to 7 days. The pharmacokinetic dose-escalation study employed IV infusions of 4.21 to 140.45 nmol/kg over 15 minutes. Neither study establishes a validated subcutaneous dose for performance or wellness applications.

In compounding practice prior to regulatory restrictions, practitioners commonly described subcutaneous doses of 200 to 300 mcg administered one to three times daily, often timed to fasting states such as before sleep or 30 to 60 minutes after exercise to align with natural GH pulsatility. Some prescribers cited weight-based guidance of 1 to 3 mcg/kg per injection as a starting range. Cycle lengths of 8 to 12 weeks appear frequently in practitioner literature; no human data establish whether cycling provides safety advantages over continuous administration.

Regulatory context in the United States: ipamorelin carries no FDA-approved indication. The FDA Pharmacy Compounding Advisory Committee voted against nominations for ipamorelin in late 2024, and the compound was placed in Category 2 on the 503B bulk drug substance list, restricting licensed outsourcing facilities from compounding it.

This information is provided for educational and reference purposes only and does not constitute medical advice. Any clinical use of ipamorelin must be determined by a licensed healthcare provider with appropriate oversight.

Lyophilized (before reconstitution)

Multiple vendor sources cite 24–36 months at −20°C for Ipamorelin lyophilized powder, with refrigerated (2–8°C) storage acceptable for shorter active-use windows. Growth-hormone secretagogues are treated as one of the more forgiving classes at this tier because the class generally lacks highly oxidation-prone residues. Keep dry, sealed, and away from light.

Reconstituted

Commonly cited at ~28 days refrigerated (2–8°C) in bacteriostatic water, with some vendor sources allowing 30–45 days. Never freeze a reconstituted vial. This is a vendor-derived convention rather than a peptide-specific stability study — the window traces to the 0.9% benzyl alcohol preservative's antimicrobial validation, not to an Ipamorelin-specific assay. See the Storage & handling primer for context.

For general storage chemistry (bacteriostatic vs sterile water, freeze-thaw, BUD framework), see Storage & handling.

Last reviewed: July 1, 2026

The most widely described combination is ipamorelin with CJC-1295, a long-acting GHRH analog. The mechanistic rationale is complementary receptor engagement: CJC-1295 acts on the GHRH receptor to stimulate GH synthesis and release, while ipamorelin acts on GHS-R1a to amplify GH pulse amplitude and suppress somatostatin. Animal model data indicate that co-administration of GHRH analogs with GHS compounds produces GH pulses of greater amplitude than either agent alone, supporting an additive or synergistic interaction at the pituitary level. However, no published human randomized trial has evaluated the CJC-1295 and ipamorelin combination for any clinical endpoint; evidence for enhanced efficacy of the stack over either agent alone in humans is anecdotal, drawn from community reports and practitioner case experience only.

Ipamorelin has also been informally combined with BPC-157 or thymosin beta-4 (TB-500) in recovery-oriented protocols. No peer-reviewed animal or human studies specifically evaluate these multi-peptide stacks, and the evidence base for them is entirely anecdotal.

Ipamorelin is not currently FDA-approved for any indication. It is generally classified as a research compound. Regulatory status varies by country.

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Reported side effects: Very well-tolerated. Rare: headache, injection site reactions

In the Phase 2 bowel resection trial (Beck et al. 2014, n=114), treatment-emergent adverse events were reported in 87.5% of ipamorelin-treated patients and 94.8% of placebo patients, with no specific event type attributed to the drug at the 0.03 mg/kg IV twice-daily dose. The Phase 1 pharmacokinetic study in 40 healthy male volunteers reported no serious adverse events.

The primary pharmacological safety advantage over earlier GHRPs is selectivity: ipamorelin does not measurably raise cortisol, ACTH, prolactin, FSH, LH, or TSH, avoiding adrenal axis perturbation, mood disturbance, and galactorrhea associated with GHRP-2 and GHRP-6.

Practitioner and community literature cites transient flushing, headache, dizziness, and injection site reactions (erythema, soreness) as possible adverse effects at subcutaneous doses. Sustained elevation of GH and IGF-1 carries theoretical risks of fluid retention, peripheral edema, and carpal tunnel syndrome consistent with known effects of exogenous GH therapy. Long-term safety data in humans are absent from published literature.

• Contraindications: active or prior malignancy (GH-axis stimulation may promote tumor growth), pituitary pathology, diabetic retinopathy, and proliferative conditions. • Pregnancy and lactation: contraindicated by default given absence of safety data. • Anti-doping: ipamorelin is prohibited by WADA under S2 (Peptide Hormones, Growth Factors, Related Substances and Mimetics); Therapeutic Use Exemptions are not granted. • Regulatory: no FDA-approved prescribing information exists for any indication.