Which is better, ipamorelin or GHRP-6?
GHRP-6 has the higher evidence grade (human_observational, from acute dosing studies), while ipamorelin is animal_only for growth hormone effects but showed better hormonal selectivity than GHRP-6 in the direct animal comparison. Regulatory status offers no tiebreak: GHRP-6 is in 503B Category 2, ipamorelin went through 503A Category 2 to a withdrawn nomination and ipamorelin acetate remains in 503B Category 2, and neither has a lawful compounding path. No human trial has compared them. [1] [2] [6] [9] [10] [12]
How do ipamorelin and GHRP-6 compare?
| Dimension | Ipamorelin | GHRP-6 |
|---|---|---|
| Structure [1] [5] | Pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH2), derived from the GHRP series. | Hexapeptide (His-D-Trp-Ala-Trp-D-Phe-Lys-NH2), the original GHRP described in 1984. |
| Direct animal comparison [1] | In conscious pigs, GH release with potency and efficacy similar to GHRP-6 (ED50 about 2.3 nmol/kg), with no rise in ACTH or cortisol even at 200 times the GH ED50. | Similar GH release but also raised ACTH and cortisol in the same study. |
| Human evidence [2] [6] [7] | One randomized trial (117 adults after bowel resection, intravenous): no significant effect on time to first tolerated meal (25.3 versus 32.6 hours, p = 0.15). No human GH data published. | Acute placebo controlled sleep study: four overnight 50 ug boluses raised GH, ACTH, cortisol, and stage 2 sleep. Oral dosing released GH in short children. |
| Evidence grade [1] [2] [6] | Animal only for GH related uses. | Human observational (acute pharmacology only, no chronic trial). |
| Appetite and metabolic effects [3] [8] [9] | Increased appetite reported anecdotally; ghrelin receptor activity also speeds gut motility, the basis of the ileus program. | Marked increase in hunger is its most consistent effect; FDA cited reduced insulin sensitivity and higher blood glucose. |
| Studied doses [2] [6] [7] | Human trial: 0.03 mg/kg intravenously twice daily for up to 7 days. No subcutaneous dose established. | Acute studies: 1 ug/kg or 4 x 50 ug intravenously; 300 ug/kg orally in children. No chronic dose established. |
| FDA compounding status [9] [10] [11] | 503A Category 2 in September 2023, nominations withdrawn in 2024 and listed as a withdrawn nomination in April 2026; ipamorelin acetate remains in 503B Category 2. | 503B Category 2 since September 2023, still listed as of April 2026; no 503A nomination or listing. |
| Note: Neither can be lawfully compounded; both are prohibited under WADA section S2. | ||
Evidence grade and regulatory status
Pulled from each peptide’s own record, so it stays in step with the peptide pages.
| Attribute | Ipamorelin | GHRP-6 |
|---|---|---|
| Class | Synthetic pentapeptide growth hormone secretagogue; selective agonist at the ghrelin receptor (GHS-R1a) | Synthetic hexapeptide growth hormone secretagogue (ghrelin receptor agonist), the first of the GHRP series |
| What it is | Growth hormone releaser acting on the hunger hormone (ghrelin) receptor; raised GH in animals and one small study in men; its only randomized trial failed. | Original lab-made growth hormone releasing peptide: raises GH and hunger in small human studies; never approved; on an FDA compounding risk list; WADA banned. |
| Evidence | Evidence: Animal-only evidence | Evidence: Human observational evidence |
| FDA status | Regulatory: Removed from Category 2 (Apr 2026) | Regulatory: Not eligible for compounding |
| Compounding | Not FDA approved for any use and never approved anywhere. FDA placed ipamorelin (free base and acetate) on the 503A Category 2 list on September 29, 2023, citing immunogenicity risk, peptide related impurities, and lack of safety data for the compounded routes. The nominators withdrew the 503A nominations in September 2024 and FDA's April 2026 update moved it to the list of nominated but withdrawn substances rather than Category 1 or the bulks list. Ipamorelin acetate also remains in 503B Category 2 (added September 29, 2023) on the FDA page current as of April 22, 2026. It was not among the peptides the Pharmacy Compounding Advisory Committee reviewed in July 2026. Because it has no active nomination, is not on the 503A bulks list, and is not a component of an approved drug, licensed 503A pharmacies and 503B outsourcing facilities have no lawful basis to compound it. | Not FDA approved for any use. FDA added GHRP-6 to the 503B Category 2 list on September 29, 2023, citing immunogenicity risk from aggregation and impurities, effects on cortisol, and increased blood glucose from reduced insulin sensitivity. As of the FDA page current to April 22, 2026, GHRP-6 remains in 503B Category 2 and has no 503A nomination, so no licensed pharmacy has a lawful basis to compound it. It was not among the peptides withdrawn from Category 2 in April 2026. |
| WADA | WADA: WADA prohibited | WADA: WADA prohibited |
| Routes | Subcutaneous injection (as sold, no human pharmacokinetic publication), Intravenous infusion (human ileus trial), Intranasal (anti-doping metabolite study only) | Intravenous bolus (research studies), Oral (one pediatric study), Subcutaneous injection (as sold, not from published trials) |
| Typical cost | Not available through licensed channels. Products sold as research chemicals are not lawful for human use and are not verified for identity or purity. | Not available through licensed US channels. Products sold as research chemicals are not lawful for human use and are not verified for identity or purity. |
| Last verified |
Has ipamorelin been tested directly against GHRP-6?
| Study | Design and population | Outcome | Grade |
|---|---|---|---|
| Ipamorelin, the first selective growth hormone secretagogue1998 PMID 9849822 | In vitro rat pituitary cell assays plus in vivo studies in anesthetized rats and conscious pigs, with GHRP-6 as comparatorRats and pigs (animal study) | Ipamorelin released GH with potency and efficacy comparable to GHRP-6 but, unlike GHRP-6, did not raise ACTH or cortisol | Evidence: Animal-only evidence |
What do ipamorelin and GHRP-6 cost?
| Dimension | Ipamorelin | GHRP-6 |
|---|---|---|
| Typical cost | Not available through licensed channels. Products sold as research chemicals are not lawful for human use and are not verified for identity or purity. | Not available through licensed US channels. Products sold as research chemicals are not lawful for human use and are not verified for identity or purity. |
| Price detail | Ipamorelin price by channel | Price index in progress |
Where a price index exists, the range is the cash price per month across branded, compounded, and telehealth channels, without insurance. The cost pages give each channel separately with its sources. Otherwise the typical cost from the peptide record is shown. Legal access depends on your state: see peptide legality by state.
Frequently asked questions
Is ipamorelin better than GHRP-6?
It may be more selective: in the animal study that introduced it, ipamorelin released as much GH as GHRP-6 without raising ACTH or cortisol. But GHRP-6 has more human data, and no human trial has compared them, so there is no evidence ipamorelin is better in people. [1] [6]
Does GHRP-6 raise cortisol?
Yes. In a placebo controlled study in healthy men, overnight GHRP-6 boluses raised ACTH and cortisol along with GH. Reviews of the class also note prolactin increases. [6] [8]
Which one causes more hunger?
GHRP-6 is known for strong appetite stimulation. Ipamorelin also acts on the ghrelin receptor and increased appetite is reported anecdotally, but no human study has measured it. [1] [8]
Can I get either one from a licensed pharmacy?
No. GHRP-6 is in 503B Category 2 with no 503A pathway, and ipamorelin has only a withdrawn 503A nomination plus a 503B Category 2 listing for the acetate, so neither can be lawfully compounded. [9] [10]
Are they detectable in drug tests?
Yes. Both are prohibited under WADA section S2, and anti-doping methods detect urinary metabolites of GHRP-6 and ipamorelin after nasal dosing. [4] [11]
Conditions studied
Sources
Numbered citations above point to these primary sources. PubMed entries link to the indexed abstract.
- [1]Raun K et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol 1998PubMed 9849822, 1998
- [2]Beck DE, Sweeney WB, McCarter MD; Ipamorelin 201 Study Group. Prospective, randomized, controlled, proof-of-concept study of the ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients. Int J Colorectal Dis 2014PubMed 25331030, 2014
- [3]Venkova K et al. Efficacy of ipamorelin, a novel ghrelin mimetic, in a rodent model of postoperative ileus. J Pharmacol Exp Ther 2009PubMed 19289567, 2009
- [4]Semenistaya E et al. Determination of growth hormone releasing peptides metabolites in human urine after nasal administration of GHRP-1, GHRP-2, GHRP-6, hexarelin, and ipamorelin. Drug Test Anal 2015PubMed 25869809, 2015
- [5]Bowers CY et al. On the in vitro and in vivo activity of a new synthetic hexapeptide that acts on the pituitary to specifically release growth hormone. Endocrinology 1984PubMed 6714155, 1984
- [6]Frieboes RM et al. Growth hormone-releasing peptide-6 stimulates sleep, growth hormone, ACTH and cortisol release in normal man. Neuroendocrinology 1995PubMed 7617137, 1995
- [7]Bellone J et al. Growth hormone-releasing effect of oral GHRP-6 administration in children with short stature. Eur J Endocrinol 1995PubMed 7581965, 1995
- [8]Camanni F, Ghigo E, Arvat E. Growth hormone-releasing peptides and their analogs. Front Neuroendocrinol 1998PubMed 9465289, 1998
- [9]FDA: Certain bulk drug substances for use in compounding may present significant safety risks (Category 2 list, content current as of April 22, 2026)FDA
- [10]FDA: Bulk drug substances used in compounding under section 503A of the FD&C Act (503A bulks list, Category 1, 2, and 3 lists, and withdrawn nominations)FDA
- [11]WADA Prohibited List, section S2 peptide hormones, growth factors, related substances and mimeticsWADA
- [12]Gobburu JV et al. Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharm Res 1999PubMed 10496658, 1999
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