Ipamorelin
updated
Ipamorelin is a five-amino-acid growth-hormone secretagogue. Small human studies show hormone release, and a 114-person postoperative-ileus trial missed its primary endpoint. No controlled trial in the cited evidence measured fat loss, muscle gain, recovery, or sleep improvement.
synthetic pentapeptide ghrelin-receptor agonist
- Development code NNC 26-0161
- Agonist at the ghrelin receptor GHS-R1a
- Human endocrine response demonstrated
- No FDA-approved ipamorelin drug
What is ipamorelin?
Ipamorelin, also called NNC 26-0161, is a synthetic pentapeptide that activates the ghrelin receptor and stimulates pituitary growth-hormone release. It is not GHRH, recombinant growth hormone, or a validated long-acting depot.
Healthy-men study · IV dose response
Human pharmacology study
Gobburu JVS et al. Pharmaceutical Research, 1999.
Healthy men received five separate 15-minute intravenous infusions. Ipamorelin produced dose-related growth-hormone release, and the reported terminal drug half-life was about two hours. The study did not test sleep, body composition, injury recovery, or long-term safety.
- Participants / model
- Healthy adult men
- Treatment
- Five intravenous ipamorelin infusions at different doses
- Study design
- Dose-escalation pharmacokinetic and pharmacodynamic study
Selectivity study · mainly animal evidence
Preclinical pharmacology study
Raun K et al. European Journal of Endocrinology, 1998.
Ipamorelin released growth hormone with less ACTH and cortisol activity than older secretagogues in the tested systems, which were mainly swine and laboratory models. No chronic human selectivity comparison was performed.
- Participants / model
- Laboratory systems and swine
- Treatment
- Ipamorelin and comparator secretagogues
- Study design
- Preclinical comparative pharmacology
What has ipamorelin shown in people?
It has shown dose-related growth-hormone release in healthy men. Its largest published efficacy trial, 114 postoperative patients, did not significantly improve the primary endpoint. The cited human trials include no controlled fat-loss, muscle-gain, recovery, or sleep outcome trial.
Did the ileus trial work?
It missed its prespecified primary endpoint. Favorable secondary measures did not test a general gut, recovery, or performance benefit.
Phase 2 RCT · primary endpoint missed
Randomized controlled trial
Bowers C et al. International Journal of Colorectal Disease, 2015.
The study randomized 114 patients after bowel resection to intravenous ipamorelin or placebo. It did not significantly shorten the primary endpoint, time to first meal, although selected secondary measures were reported as favorable. It supplies no efficacy or dosing data for outpatient peptide use.
- Participants / model
- 114 adults after partial small- or large-bowel resection
- Treatment
- Intravenous ipamorelin or placebo
- Follow-up
- Postoperative inpatient treatment
- Study design
- Randomized, double-blind, placebo-controlled Phase 2 trial
Healthy-men study · IV dose response
Human pharmacology study
Gobburu JVS et al. Pharmaceutical Research, 1999.
Healthy men received five separate 15-minute intravenous infusions. Ipamorelin produced dose-related growth-hormone release, and the reported terminal drug half-life was about two hours. The study did not test sleep, body composition, injury recovery, or long-term safety.
- Participants / model
- Healthy adult men
- Treatment
- Five intravenous ipamorelin infusions at different doses
- Study design
- Dose-escalation pharmacokinetic and pharmacodynamic study
Phase 2 RCT · primary endpoint missed
Randomized controlled trial
Bowers C et al. International Journal of Colorectal Disease, 2015.
The study randomized 114 patients after bowel resection to intravenous ipamorelin or placebo. It did not significantly shorten the primary endpoint, time to first meal, although selected secondary measures were reported as favorable. It supplies no efficacy or dosing data for outpatient peptide use.
- Participants / model
- 114 adults after partial small- or large-bowel resection
- Treatment
- Intravenous ipamorelin or placebo
- Follow-up
- Postoperative inpatient treatment
- Study design
- Randomized, double-blind, placebo-controlled Phase 2 trial
Is ipamorelin selective for growth hormone?
Preclinical comparisons found less ACTH and cortisol release than older secretagogues, but the strongest selectivity claim comes mainly from animal models. Chronic human endocrine selectivity has not been established.
The studies measured a transient growth-hormone pulse. They did not show that repeated exposure improves symptoms or function, or avoids glucose, appetite, fluid, or other endocrine effects.
Selectivity study · mainly animal evidence
Preclinical pharmacology study
Raun K et al. European Journal of Endocrinology, 1998.
Ipamorelin released growth hormone with less ACTH and cortisol activity than older secretagogues in the tested systems, which were mainly swine and laboratory models. No chronic human selectivity comparison was performed.
- Participants / model
- Laboratory systems and swine
- Treatment
- Ipamorelin and comparator secretagogues
- Study design
- Preclinical comparative pharmacology
Healthy-men study · IV dose response
Human pharmacology study
Gobburu JVS et al. Pharmaceutical Research, 1999.
Healthy men received five separate 15-minute intravenous infusions. Ipamorelin produced dose-related growth-hormone release, and the reported terminal drug half-life was about two hours. The study did not test sleep, body composition, injury recovery, or long-term safety.
- Participants / model
- Healthy adult men
- Treatment
- Five intravenous ipamorelin infusions at different doses
- Study design
- Dose-escalation pharmacokinetic and pharmacodynamic study
What are the material safety limits?
The IV development program supplies some monitored exposure, but serious events occurred in a sick postoperative population and attribution is uncertain. Safety for chronic subcutaneous use, combinations, pregnancy, immune reactions, and unregulated products remains inadequately characterized.
- Causality: the postoperative trial reports do not establish that ipamorelin caused the deaths or serious events, but those events remain part of the human safety record.
- Endocrine effects: repeated GH and IGF-1 stimulation may affect glucose, edema, appetite, and symptoms in susceptible people.
- Product quality: nonstandard products add potency, sterility, endotoxin, and peptide-impurity risk.
Phase 2 RCT · primary endpoint missed
Randomized controlled trial
Bowers C et al. International Journal of Colorectal Disease, 2015.
The study randomized 114 patients after bowel resection to intravenous ipamorelin or placebo. It did not significantly shorten the primary endpoint, time to first meal, although selected secondary measures were reported as favorable. It supplies no efficacy or dosing data for outpatient peptide use.
- Participants / model
- 114 adults after partial small- or large-bowel resection
- Treatment
- Intravenous ipamorelin or placebo
- Follow-up
- Postoperative inpatient treatment
- Study design
- Randomized, double-blind, placebo-controlled Phase 2 trial
FDA safety page · limited route data
FDA safety communication
US Food and Drug Administration.
FDA cites immunogenicity and impurity concerns, limited safety information for proposed routes, and serious adverse events in the intravenous postoperative-ileus development program. These reports do not establish that ipamorelin caused each event or that an IV event rate applies to other routes.
- Study design
- Agency safety summary
Is ipamorelin approved?
The cited FDA records list no approved ipamorelin drug. FDA lists compounding safety concerns, and WADA prohibits growth-hormone secretagogues for covered athletes.
FDA safety page · limited route data
FDA safety communication
US Food and Drug Administration.
FDA cites immunogenicity and impurity concerns, limited safety information for proposed routes, and serious adverse events in the intravenous postoperative-ileus development program. These reports do not establish that ipamorelin caused each event or that an IV event rate applies to other routes.
- Study design
- Agency safety summary
WADA 2026 · growth-hormone secretagogues
Sports rule
World Anti-Doping Agency, effective 1 January 2026.
Growth-hormone secretagogues, including ghrelin mimetics, are prohibited under S2 for athletes covered by the Code.
- Study design
- Binding sport rule for covered athletes
Studies and sources
Healthy-men study · IV dose response
Human pharmacology study
Gobburu JVS et al. Pharmaceutical Research, 1999.
Healthy men received five separate 15-minute intravenous infusions. Ipamorelin produced dose-related growth-hormone release, and the reported terminal drug half-life was about two hours. The study did not test sleep, body composition, injury recovery, or long-term safety.
- Participants / model
- Healthy adult men
- Treatment
- Five intravenous ipamorelin infusions at different doses
- Study design
- Dose-escalation pharmacokinetic and pharmacodynamic study
Phase 2 RCT · primary endpoint missed
Randomized controlled trial
Bowers C et al. International Journal of Colorectal Disease, 2015.
The study randomized 114 patients after bowel resection to intravenous ipamorelin or placebo. It did not significantly shorten the primary endpoint, time to first meal, although selected secondary measures were reported as favorable. It supplies no efficacy or dosing data for outpatient peptide use.
- Participants / model
- 114 adults after partial small- or large-bowel resection
- Treatment
- Intravenous ipamorelin or placebo
- Follow-up
- Postoperative inpatient treatment
- Study design
- Randomized, double-blind, placebo-controlled Phase 2 trial
Selectivity study · mainly animal evidence
Preclinical pharmacology study
Raun K et al. European Journal of Endocrinology, 1998.
Ipamorelin released growth hormone with less ACTH and cortisol activity than older secretagogues in the tested systems, which were mainly swine and laboratory models. No chronic human selectivity comparison was performed.
- Participants / model
- Laboratory systems and swine
- Treatment
- Ipamorelin and comparator secretagogues
- Study design
- Preclinical comparative pharmacology
FDA safety page · limited route data
FDA safety communication
US Food and Drug Administration.
FDA cites immunogenicity and impurity concerns, limited safety information for proposed routes, and serious adverse events in the intravenous postoperative-ileus development program. These reports do not establish that ipamorelin caused each event or that an IV event rate applies to other routes.
- Study design
- Agency safety summary
WADA 2026 · growth-hormone secretagogues
Sports rule
World Anti-Doping Agency, effective 1 January 2026.
Growth-hormone secretagogues, including ghrelin mimetics, are prohibited under S2 for athletes covered by the Code.
- Study design
- Binding sport rule for covered athletes
Why is Ipamorelin in C tier?
C reflects dose-related human growth-hormone release plus a 114-person clinical efficacy trial that missed its primary endpoint. No controlled study measured the marketed fitness, recovery, or sleep outcomes.
read Ipamorelin in the reptides guide, chapter 06: 8 pages, free to read.