Ipamorelin Peptide

## What it is Ipamorelin is a synthetic pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH2) developed by Novo Nordisk in the 1990s under the code NNC 26-0161 as a selective growth-hormone secretagogue. The sequence was engineered to retain potent activity at GHS-R1a (the ghrelin receptor) while minimizing the off-target cortisol and prolactin elevation typical of GHRP-2, GHRP-6, and hexarelin. The result is the cleanest selectivity profile of any peptide in the GHRP class. The compound was advanced by Helsinn through phase 2 trials in postoperative ileus (Greenwood-Van Meerveld 2010) and reached phase 2b before being discontinued in 2012 after the larger phase 2 readout did not meet primary endpoints. It was never approved for any indication. WADA places ipamorelin on the Prohibited List under S2 (peptide hormones, growth factors). Distribution today is via research-peptide vendors. The user base is the largest of any synthetic GHRP, predominantly body-composition focused athletes, anti-aging clinic patients, and biohackers pursuing recovery and sleep effects. The clean side-effect profile is the practical reason it dominates the GHRP market over GHRP-2 and GHRP-6. ## Mechanism of action Ipamorelin binds GHS-R1a with high affinity and stimulates pulsatile GH release through the standard ghrelin-receptor pathway: suppression of hypothalamic somatostatin and direct stimulation of pituitary somatotrophs. The acute GH pulse is smaller than GHRP-2 or hexarelin at equivalent molar doses but the selectivity profile is the cleanest in the class. The defining pharmacologic feature is what ipamorelin does not do. Cortisol and prolactin elevation in human acute-dosing studies are minimal to undetectable at standard doses, which is mechanistically attributable to the modified sequence's reduced cross-activation of ACTH and prolactin pathways. Insulin secretion is not appreciably stimulated. The acute appetite effect is mild, less pronounced than GHRP-6 and noticeably less than GHRP-2. Plasma half-life is approximately 2 hours, longer than GHRP-2, GHRP-6, or hexarelin. The longer pharmacokinetic profile produces a more sustained GH response per dose and tolerates less aggressive multi-daily dosing schedules. ## Evidence base The ipamorelin clinical trial base is the most substantial of any synthetic GHRP. Helsinn's phase 2 program in postoperative ileus included multiple controlled trials totaling several hundred participants, generating the bulk of the modern human safety and PK data. The phase 2b readout in 2012 (Beck 2014) did not meet primary endpoints for time-to-recovery from postoperative ileus, but the safety database was substantial and consistent. Human GH provocation studies (Raun 1998, Gobburu 1999) established the acute GH response profile in healthy adults: dose-dependent GH peak at 1 to 100 mcg/kg, no clinically significant cortisol or prolactin rise at therapeutic doses. Multi-week dosing in healthy older adults has been studied in small trials (n under 50 per arm) showing sustained IGF-1 elevation of roughly 1.5 to 2 fold over 4 to 8 weeks. Direct body-composition trials in adults are sparse. The only completed RCT-grade work is repurposed from the postoperative ileus program and the GH-deficiency provocation literature. The body-composition use case rests on anecdotal protocols and inference from the IGF-1 axis activation; controlled trials specifically powered for lean-mass and fat-loss endpoints have not been completed. The combined CJC-1295 plus ipamorelin protocol popular in anti-aging clinics is unsupported by controlled human trials. The mechanism (GHRH plus ghrelin parallel stimulation) is well-grounded but the specific clinical outcomes of the combination have not been measured in completed trials. ## Dosage and administration Research-protocol dosing typically runs 200 to 300 mcg subcutaneously 2 to 3 times daily, timed pre-bed, mid-morning, and post-workout to align with endogenous GH pulse windows. Pre-bed dosing produces the most consistent subjective effect on sleep depth. The longer ipamorelin half-life (2 hours vs 30 to 60 minutes for other GHRPs) makes once-daily dosing meaningful for some users, though multi-daily dosing produces a more physiologic pulse architecture. A typical 5 mg vial reconstituted with 2 mL bacteriostatic water gives 2.5 mg/mL. A 200 mcg dose draws 8 units on a U100 insulin syringe. Ipamorelin is the standard pairing for CJC-1295 no-DAC (Mod GRF 1-29), with both peptides typically combined in the same syringe at the same time point for synergistic GH release. Anecdotal cycles run 8 to 12 weeks on, then 4 weeks off. Fasted dosing with a 30 to 60 minute window before food preserves the GH pulse; circulating glucose and free fatty acids suppress GH release. ## Side effects and safety The defining feature is the clean profile: minimal hunger pulse, no clinically significant cortisol or prolactin rise at standard doses, low water retention compared to other GHRPs. Reported side effects are mostly mild: occasional injection-site irritation, vivid dreams when dosed pre-bed, transient mild head pressure or flushing in early dosing, and rare headache. The phase 2 ileus program (n approximately 600 across studies) provides the most substantial human safety database in the GHRP class. Adverse events in those trials were predominantly mild GI and headache, broadly consistent with the placebo arm. No serious GH-axis adverse events were reported. Long-term safety at chronic body-composition doses (years of multi-daily dosing) is not formally characterized. Theoretical concerns mirror the rest of the class: insulin resistance with sustained GH elevation (track fasting glucose and HbA1c), theoretical malignancy concern via IGF-1 axis activation, and pituitary downregulation with continuous use. Contraindications on mechanistic grounds include pregnancy, active malignancy, history of pituitary tumor, and uncontrolled diabetes. Athletes face WADA sanctions; detection methods are validated. ## Practical notes Lyophilized ipamorelin is stable at room temperature for the labeled shelf life and should be refrigerated for longer storage. Reconstituted vials should be refrigerated and used within 4 weeks. Bacteriostatic water is the standard reconstitution medium. For the body-composition use case, ipamorelin is the most defensible default in the GHRP class: cleanest selectivity profile, largest human safety database, longest half-life supporting more practical dosing schedules. The trade-off is the smaller acute GH pulse than GHRP-2 or hexarelin, and the absence of the appetite-stimulation feature that some users actively want from GHRP-6. Measurable IGF-1 elevation typically appears within 2 to 4 weeks of consistent multi-daily dosing. Subjective sleep deepening from pre-bed dosing usually appears within the first week. If labs at 6 to 8 weeks show no IGF-1 movement, the vial is most likely under-dosed or inactive, a recurring problem in unregulated supply chains. Body-composition changes, if any, accumulate over 8 to 12 weeks and require concurrent training and nutrition to be detectable above baseline.