Educational reference only. Informational material drawn from peer-reviewed literature. Not medical advice and not a recommendation to use, dose, or modify any therapy. Decisions about hormone therapy should be made with a qualified healthcare provider.
Overview
Overview
GHRP-2 (generic name pralmorelin, international nonproprietary name; brand name GHRP Kaken 100) is a synthetic hexapeptide that functions as a growth hormone secretagogue receptor (GHS-R1a) agonist. It belongs to the same pharmacological class as ipamorelin, GHRP-6, and hexarelin (the GHRPs, or ghrelin mimetics), but holds a unique distinction: GHRP-2 is the only growth hormone secretagogue ever approved by any national regulatory authority for human use.
Japan's Pharmaceuticals and Medical Devices Agency (PMDA) approved pralmorelin in October 2004 as a diagnostic agent for assessing growth hormone deficiency in adults and children over four years old.
The Japanese approval is important context but commonly misunderstood. It is approval for diagnostic use only: a single-dose intravenous test to evaluate GH deficiency, not approval for therapeutic, anti-aging, or muscle-building use. No regulatory authority has approved any GHRP for therapeutic use.
GHRP-2 has a substantial clinical research history including Phase II/III trials in Japan and additional studies in the United States and Europe. It was originally developed by Polygen and collaborators at Tulane University in the 1990s, then licensed to Kaken Pharmaceutical (which retains rights in Japan) and sublicensed to Wyeth (American Home Products) for the United States and Canada. The North American development never advanced to FDA approval.
Forms
Available forms & half-lives
| Form | Approximate half-life |
|---|---|
| Subcutaneous GHRP-2 | ~15–60 minutes (bi-exponential) |
| Intravenous GHRP-2 | ~10–20 minutes |
| Oral / intranasal GHRP-2 | Variable; lower bioavailability |
What it does
Main effects
- Diagnostic GH stimulation testing: Japan PMDA-approved 2004 indication; 1 mcg/kg IV single dose; GH response >15 mcg/L = intact GH secretion, <15 mcg/L = severe deficiency (validated cutoff) PMID: 15230633
- Highest GH-releasing potency of the major GHRPs: produces greater peak GH levels than ipamorelin at comparable doses; the potency vs selectivity trade-off is the central pharmacological difference between these two GHRPs
- GHS-R1a (ghrelin receptor) agonism on pituitary somatotrophs, the same fundamental mechanism as ipamorelin, GHRP-6, and hexarelin
- Separate receptor pathway from GHRH: GHS-R1a agonism and GHRH receptor activation are distinct mechanisms converging on the same pituitary somatotrophs, so the two pathways interact
- Pediatric clinical evidence in pituitary dwarfism from Japanese Phase 2 trials; 8-month pediatric study (Mericq et al., PMID 9543135) demonstrated sustained GH-related parameter increases with no side effects/toxicities at any tested dose
- Intranasal administration feasibility: intranasal delivery produced measurable GH elevations in the 8-month pediatric study (Mericq et al. 1998) PMID: 9543135
- Most clinically validated GHRP: 3–5 RCTs, only national regulatory approval (Japan) of any GHRP
- CD36 binding (less prominent than GHRP-6): may contribute to cardiovascular and fatty acid metabolism effects
- Moderate appetite stimulation: less than GHRP-6 but more than ipamorelin
What to watch for
Common side effects
- Injection site reactions (pain, redness, swelling): most common adverse effect; mild and self-limited
- Mild constitutional symptoms (flushing common with initial doses, headache, occasional mild fatigue)
- Moderate cortisol/ACTH elevation: more than ipamorelin, less than GHRP-6; clinical implications include possible weight gain with chronic use, mood effects, glucose dysregulation, theoretical immunosuppression, possible bone density effects long-term
- Moderate prolactin elevation: less prominent than GHRP-6 but more than ipamorelin; possible galactorrhea, gynecomastia in men, sexual dysfunction, fertility effects with chronic use
- Moderate appetite stimulation: desired for cachexia/weight gain indications; undesired for body composition or weight loss goals
- Mild insulin resistance with chronic use: combined GH + cortisol effects may produce more glucose dysregulation than ipamorelin; caution in diabetic patients
- IGF-1 elevation with chronic use: monitoring recommended; theoretical cancer concerns with sustained elevation
- No significant adverse cardiovascular signal in available trials
- Limited multi-year adult safety data: longest published human trials are 6–12 months in pediatric subjects; non-medical chronic adult use not systematically tracked
- FDA has issued warning letters to pharmacies marketing GHRP-2 for human administration, a more aggressive US regulatory stance than for some other unapproved peptides
- The Japanese diagnostic-only approval does NOT validate therapeutic/anti-aging/muscle-building use. Marketing of GHRP-2 as "approved by Japan" is misleading when applied to chronic use
- WADA-prohibited under category S2
Key facts
Key facts worth knowing
- GHRP-2 is a synthetic hexapeptide (6 amino acids) with sequence D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH₂ (MW 817.95 Da). Like ipamorelin, it incorporates non-natural amino acids (D-isomers and D-2-naphthylalanine) for stability and receptor selectivity.
- Japan PMDA approval (October 2004) for diagnostic use only. Marketed as GHRP Kaken 100 by Kaken Pharmaceutical for assessment of GH deficiency in adults and children ≥4 years old. This is the only national regulatory approval of any GHRP globally. PMID: 15230633
- Mechanism is GHS-R1a (ghrelin receptor) agonism, the same fundamental mechanism as ipamorelin, GHRP-6, and hexarelin. Distinguished by its higher absolute GH-releasing potency than ipamorelin combined with moderate off-target effects.
- Selectivity profile is intermediate between ipamorelin (cleanest) and GHRP-6 (least selective): GHRP-2 produces moderate ACTH/cortisol elevation (less than GHRP-6, more than ipamorelin), moderate prolactin elevation, and less appetite stimulation than GHRP-6 but more than ipamorelin.
- Higher GH-releasing potency than ipamorelin: GHRP-2 produces greater peak GH levels than ipamorelin at comparable doses, alongside more cortisol, prolactin and appetite effect. This potency vs selectivity trade-off is the central pharmacological difference between these two GHRPs.
- Pediatric clinical evidence from Japan demonstrated efficacy in pituitary dwarfism in Phase 2 trials. The 8-month pediatric study (Mericq et al., PMID 9543135) demonstrated sustained GH-related parameter increases with no side effects or toxicities at any dose level tested, one of the longer-duration human GHRP studies. PMID: 9543135
- Multiple human clinical trials exist (3–5 RCTs), making GHRP-2 the most clinically validated GHRP in terms of regulatory and trial history. North American development by Wyeth for pediatric GH deficiency did not advance to FDA approval (commercial decisions; Wyeth was acquired by Pfizer in 2009).
- WADA Prohibited under category S2. FDA has issued warning letters to pharmacies marketing GHRP-2 for human administration.
Legal status
Legal status
Approved in Japan for diagnostic use (since 2004) as GHRP Kaken 100 (Kaken Pharmaceutical). Not FDA-approved in the United States. FDA has issued warning letters to pharmacies marketing GHRP-2 for human administration. Some compounding pharmacies supply it, with evolving regulatory status. Not a controlled substance. WADA-prohibited under category S2.