What it is
Ipamorelin is a synthetic five amino acid peptide that mimics ghrelin, the stomach hormone that also acts as a growth hormone signal. Its discovery was published in 1998: it came from screening relatives of the older GH-releasing peptides that lacked the central alanine-tryptophan pair of GHRP-1.
Its selling point from the start was selectivity. Earlier GH-releasing peptides such as GHRP-6 and GHRP-2 also raise ACTH and cortisol. In the original animal work, ipamorelin did not.
How it works
Ipamorelin binds the growth hormone secretagogue receptor (GHS-R1a), the receptor ghrelin uses. This is a different receptor from the one GHRH analogues such as CJC-1295 and sermorelin act on. Activation in the pituitary releases a pulse of GH, and GH raises IGF-1.
Because the two receptors are separate, a ghrelin mimetic and a GHRH analogue can be combined. In a 1990 study in healthy men, a GH-releasing peptide plus GHRH released GH synergistically. That is the logic behind CJC-1295 + ipamorelin.
The ghrelin receptor also sits in the gut, where it speeds up movement of the stomach and intestines. That gut effect is why ipamorelin's only patient trial was in bowel surgery.
What the research found
Human studies
Gobburu and colleagues (1999) gave healthy men a single 15-minute IV infusion at five dose levels, eight men per level. The drug behaved predictably across doses:
- terminal half-life of about 2 hours
- a single episode of GH release at every dose, peaking at about 0.67 hours (roughly 40 minutes) and then declining to negligible levels
- more person-to-person variation in the GH response than in blood levels of the drug
Beck and colleagues (2014) ran a Phase 2, double-blind, placebo-controlled trial in adults recovering from bowel resection, testing whether ipamorelin would speed return of gut function. Of 117 patients enrolled, 114 were analysed. Median time to the first tolerated solid meal was 25.3 hours with ipamorelin and 32.6 hours with placebo, a difference that was not statistically significant (p = 0.15). Secondary endpoints also showed no difference. The drug was well tolerated: adverse events occurred in 87.5% of the ipamorelin group and 94.8% of the placebo group, reflecting post-surgical patients.
After that trial, clinical development was discontinued.
Animal and lab studies
Raun and colleagues (1998) described ipamorelin's discovery. In rat pituitary cells and in anaesthetised rats it released GH with potency and efficacy similar to GHRP-6. In conscious pigs:
- it did not change FSH, LH, prolactin or TSH
- GHRP-6 and GHRP-2 raised ACTH and cortisol; ipamorelin did not, even at doses more than 200 times higher than those needed for GH release
That is the source of the "clean GH release" claim. It is an animal finding, not one confirmed in a human trial.
Side effects reported in studies
The human data is thin: single infusions in healthy men, and a week of twice-daily IV dosing in surgical patients, where the drug was well tolerated and adverse events were no more common than on placebo.
The US FDA's 2024 review for its compounding advisory committee found no credible evidence of benefit for GH deficiency or postoperative ileus, and listed its concerns: incomplete characterisation of impurities and aggregation, minimal toxicology data, a possible reinforcing effect through the ghrelin receptor, and possible effects on fertility and fetal development. The FDA also flags a risk of immunogenicity from aggregation or impurities in compounded ipamorelin.
Like any GH secretagogue, ipamorelin raises IGF-1, and ghrelin receptor agonists can increase appetite.
Ipamorelin vs other GH secretagogues
| Compound | Receptor | ACTH and cortisol | Human data |
|---|---|---|---|
| Ipamorelin | Ghrelin (GHS-R1a) | Not raised in animal tests | PK study; Phase 2 in surgery |
| GHRP-6 | Ghrelin | Raises ACTH and cortisol in pigs | Small human studies |
| GHRP-2 | Ghrelin | Raises ACTH and cortisol in pigs | Small human studies |
| MK-677 | Ghrelin | Cortisol rose in a 2-year trial | Oral; trials up to 2 years |
| CJC-1295 no DAC | GHRH | Not applicable | None published |
Status in the Philippines
No ipamorelin product is registered with FDA Philippines, and it has never been approved in any country. It is not a controlled substance under RA 9165. In the US, FDA advisers reviewed it in October 2024 and the agency recommended against adding it to the list of substances pharmacies may compound. Locally it is one of the most commonly sold GH peptides, often supplied pre-mixed with CJC-1295.
Local stock CJC-1295 + Ipamorelin 10mg at Primara Labs, delivered in Metro Manila and nationwide. Research use only.
Storage
Store the freeze-dried powder in the refrigerator. After mixing with bacteriostatic water, keep it at 2 to 8°C and protect it from light. During brownouts, move vials to a cooler with ice packs rather than leaving them in a warm fridge. The ipamorelin calculator handles reconstitution arithmetic.
