Ipamorelin: Side Effects

Safety Notice#

The safety profile of Ipamorelin in humans has not been established through controlled clinical trials. The information below is derived primarily from animal studies and should be interpreted accordingly.

Documented Adverse Effects#

Objective and method We searched peer‑reviewed articles and registered trials for ipamorelin (a selective ghrelin/GHSR agonist) to extract adverse effects in animals and humans, including frequencies and severities where reported. Evidence was gathered from a randomized controlled human trial and reviews summarizing preclinical findings.

Findings Animal studies

• Mouse models: Ipamorelin increased adiposity (higher total body fat percentage and fat pad weights), increased cumulative food intake during the first week, and raised leptin; importantly, no organomegaly (e.g., liver enlargement) was observed in contrast to exogenous GH comparators. Frequency/incidence per animal were not reported; effects were phenotypic/metabolic and not overt toxicity (no organ toxicity signals noted in the excerpt).
• Rat study (as cited in a review): Daily subcutaneous ipamorelin at 0.5 mg/kg was reported as safe, with no clinical or genetic toxicity observed in rats. Frequency data were not provided.
• GLP toxicology: We did not retrieve dedicated GLP toxicology reports in this search; a development review notes that discontinuation of ipamorelin for gastrointestinal indications was due to lack of efficacy, not reported toxicity.

Human studies

• Phase 2 randomized, double‑blind, placebo‑controlled proof‑of‑concept trial in postoperative bowel‑resection patients (ipamorelin 0.03 mg/kg IV twice daily, postoperative day 1–7): • Any treatment‑emergent adverse event (TEAE): 87.5% (49/56) ipamorelin vs 94.8% (55/58) placebo. • Adverse events considered related to study drug: 30.4% ipamorelin vs 36.2% placebo. • Severity distribution (by event, ipamorelin): mild 33.9%, moderate 46.4%, severe 7.1%. • Common TEAEs in ipamorelin arm with frequencies: nausea 33.9% (19/56), vomiting 28.6% (16/56), abdominal distension 19.6% (11/56), pyrexia 17.9% (10/56), tachycardia 14.3% (8/56), ileus 12.5% (7/56), hypokalemia 12.5% (7/56); insomnia occurred >5% more often than placebo (exact percentage not given in excerpt). • Laboratory/physiologic shifts: greater shift to high blood glucose at discharge with ipamorelin (14.3%) vs placebo (8.6%). • Serious adverse events (SAEs): 17.9% (10 patients) ipamorelin vs 15.5% (9 patients) placebo; anastomotic leaks were the most common SAE (3.6% vs 1.7%). Two fatal SAEs occurred in the ipamorelin arm (both anastomotic leaks) and were judged possibly related by investigators; many SAEs occurred after completion of ipamorelin. • Discontinuations due to AEs: 5.4% (3/56) ipamorelin (nausea, hypertension, hypotension) vs 5.2% (3/58) placebo. • Overall tolerability: Authors judged ipamorelin “well tolerated,” and many events likely reflected postoperative status/underlying disease.

Synthesis and interpretation

• Animals: Available preclinical reports indicate metabolic effects consistent with ghrelin receptor agonism (increased appetite/adiposity) without organ enlargement in mice and with a rat study noting no clinical/genotoxic toxicity at 0.5 mg/kg/day SC. Quantitative incidence and severity grading were not reported in the retrieved animal sources.
• Humans: In postoperative ileus Phase 2, overall AE rates were high in both arms, typical of the postoperative setting. Ipamorelin’s common AEs included gastrointestinal symptoms (nausea, vomiting, abdominal distension), pyrexia, tachycardia, ileus, and hypokalemia, largely mild–moderate; severe events comprised 7.1% by event. SAEs (including two fatal anastomotic leaks possibly related) occurred at similar patient-level frequency to placebo, but attribution is uncertain given surgical context. Small sample size limits precision.

Concise summary artifact

Limitations

• We did not retrieve formal GLP toxicology packages; animal frequency/severity data are sparse. Human data derive mainly from a single Phase 2 postoperative trial; additional Phase 2 trial results (NCT01280344) were not available in the retrieved texts.

Conclusion

• Animal studies: Ipamorelin has been associated with increased appetite/adiposity and leptin without organomegaly in mice; a cited rat study at 0.5 mg/kg/day SC reported no clinical or genetic toxicity. Frequency/severity not quantified.
• Human reports: In a Phase 2 trial (0.03 mg/kg IV BID up to 7 days), any TEAEs occurred in 87.5% of ipamorelin‑treated patients; common AEs were nausea (33.9%), vomiting (28.6%), abdominal distension (19.6%), pyrexia (17.9%), tachycardia (14.3%), ileus (12.5%), hypokalemia (12.5%); severity distribution mild 33.9%, moderate 46.4%, severe 7.1%; SAEs in 17.9% with two fatal postoperative anastomotic leaks possibly related; discontinuations due to AEs 5.4%. A shift to high blood glucose was more frequent with ipamorelin (14.3%) than placebo (8.6%). These data reflect a postoperative population and should be interpreted in that context.

Contraindications#

Ipamorelin is a selective ghrelin (GHSR‑1a) agonist that increases GH pulsatility and can raise IGF‑1, with additional prokinetic actions in the gastrointestinal tract. Formal, label‑level contraindications are not established because ipamorelin is investigational; therefore, practical contraindications are inferred from clinical‑trial exclusions and class safety signals, and drug–drug interactions are derived from available class data and mechanism.

Observed or trial‑inferred contraindications/precautions

• Pregnancy: excluded from clinical trials; avoid use given unknown fetal risk (NCT00672074, NCT01280344).
• Significant hepatic or renal impairment: excluded when ALT/total bilirubin above limits or creatinine >2.5 mg/dL; use is contraindicated/precautionary in significant dysfunction (NCT01280344, NCT00672074).
• Clinically significant ECG or laboratory abnormalities/clinically unstable status: excluded in trials; use caution or avoid (NCT00672074, NCT01280344).
• Specific gastrointestinal histories/anatomy in POI context: prior complex GI surgeries, colonic volvulus, extensive IBD surgery/radiation were excluded; context‑specific precaution (NCT01280344).

Class effects informing precautions and theoretical contraindications

• Glucose metabolism: GHSR agonists elevate IGF‑1 and can worsen insulin sensitivity; multiple trials of related agents report increased fasting glucose/HbA1c and impaired glucose tolerance. Patients with diabetes or prediabetes require monitoring and potential adjustment of antidiabetic therapy.
• Cardiovascular disease/heart failure: A randomized trial of the GHS ibutamoren showed a higher rate of congestive heart failure; ghrelin/GHSR agonists can acutely alter vascular resistance and cardiac output. Use caution in heart failure or significant CVD, monitor BP/volume status and potential interactions with antihypertensives/diuretics.
• Active malignancy: Sustained increases in GH/IGF‑1 are mitogenic; long‑term oncologic safety of chronically elevating IGF‑1 with GHSs is uncertain. Consider avoidance in active cancer unless benefit outweighs risk (theoretical).

Drug–drug interactions (observed/class‑informed and mechanistic/theoretical)

• Antidiabetic medications (insulin, metformin, sulfonylureas, GLP‑1 RAs, SGLT2 inhibitors): ipamorelin may raise glucose via GH/IGF‑1–mediated insulin resistance; monitor glycemia and adjust antidiabetic doses as needed (class clinical data).
• Agents affecting GI motility and absorption: other prokinetics (e.g., metoclopramide, prucalopride) may have additive effects; anticholinergics and opioids may blunt prokinetic benefit. Changes in transit can alter absorption of oral drugs with narrow therapeutic windows (mechanistic/clinical rationale).
• GHRH analogs and somatostatin analogs: GHRH analogs can synergize GH release with GHSR agonists; somatostatin analogs may blunt GH release and counteract effect (mechanistic/class data).
• Corticosteroids: preclinical data indicate ipamorelin can mitigate glucocorticoid‑induced muscle/bone effects, but combined use can exacerbate insulin resistance and hyperglycemia; monitor metabolic parameters (preclinical/class).
• Cardiovascular agents (antihypertensives, diuretics): given potential hemodynamic effects of ghrelin agonism, monitor for hypotension, edema, or CHF exacerbation; adjust therapy as needed (class/theoretical).
• CYP‑mediated interactions: another GHS (tabimorelin) inhibited CYP3A4 and interacted with midazolam; specific CYP interactions for ipamorelin are not reported—treat as low‑likelihood but remain vigilant with sensitive CYP3A4 substrates (class extrapolation).
• Other pituitary‑axis drugs: ipamorelin appears selective without ACTH/cortisol stimulation in swine, suggesting lower risk of interactions involving glucocorticoid replacement, though class heterogeneity exists; monitor clinically (preclinical/class).

Embedded summary table

• Contraindications are not label‑defined; avoid in pregnancy and in patients meeting trial exclusion profiles (significant hepatic/renal dysfunction, unstable cardiac/ECG or lab abnormalities), and use caution in complex GI anatomy when used for postoperative ileus (NCT00672074, NCT01280344).
• Key interaction domains arise from GH/IGF‑1 elevation (glycemic worsening), GI prokinetic effects (absorption/antagonism with opioids/anticholinergics), and potential cardiovascular effects; limited long‑term safety data warrant conservative monitoring and individualized risk–benefit assessment.

Toxicology#

Objective evidence was located primarily in two US patents describing preclinical and early clinical work with ipamorelin, plus Phase II clinical trial registry entries. These sources provide acute toxicity signals, pharmacodynamic dose–response observations, and clinical dose ranges, but they do not report formal LD50 values, organ‑specific toxicology, or genotoxicity assays. Where data are missing, this is indicated explicitly below.

• Acute toxicity/LD50 • Rat, IV: Immediate lethality occurred in 2 animals given 10 mg/kg; the cohort was subsequently dose‑reduced to 0.25 mg/kg. A formal LD50 was not determined in the retrieved texts.

• Organ toxicity (liver, kidney, cardiac, etc.) • No organ‑specific histopathology or target‑organ toxicities were reported in the retrieved patent examples; studies were focused on GI pharmacology. Clinical trial registry text did not include organ‑specific adverse‑event summaries.

• Mutagenicity/genotoxicity • No Ames, micronucleus, or chromosomal aberration test results were identified in the retrieved documents.

• Dose–response relationships (preclinical) • Rat, IV, post‑operative ileus models: Ipamorelin accelerated gastric emptying at multiple doses, but the pharmacodynamic response was non‑monotonic across 0.01–2.5 mg/kg. In one experiment, 0.25 and 2.5 mg/kg produced similar efficacy (~50–60% reduction in stomach phenol‑red content), whereas 1 mg/kg produced a smaller effect (~21%). Lower doses (0.01–0.1 mg/kg) also improved gastric emptying versus controls, with statistical significance reported in these experiments.

• Human clinical safety and dose ranges • Healthy volunteers: Ipamorelin 0.06 mg/kg IV infused over 15 minutes was described as well tolerated and reversed morphine‑induced slowing of gastric emptying in a crossover study; additional data at 0.01 and 0.03 mg/kg also showed reversal of morphine effects. • Surgical patients (Phase II): Two completed randomized studies evaluated 0.03–0.06 mg/kg regimens (BID or TID) for postoperative GI recovery; registry entries list safety/tolerability as outcomes but do not contain detailed adverse‑event results in the accessed text (NCT01280344, NCT00672074).

• An acute lethal signal after 10 mg/kg IV in rats indicates a substantial safety margin is unlikely at very high bolus doses; however, because a full LD50 determination was not presented, quantitative LD50 remains undetermined in the retrieved record.

• Across 0.01–2.5 mg/kg IV in rats, ipamorelin’s GI prokinetic effect does not scale linearly with dose; similar efficacy at 0.25 and 2.5 mg/kg and a trough at 1 mg/kg suggest complex dose–response dynamics, possibly reflecting pharmacology of ghrelin‑receptor pathways or experimental variability.

• No genotoxicity or formal organ‑toxicity studies were found in the accessed material; absence of evidence here should not be interpreted as evidence of absence. Phase II exposure in humans at 0.03–0.06 mg/kg supports short‑term tolerability, but organ‑specific safety conclusions cannot be drawn from the registry text alone.

• Preclinical rat studies and early human volunteer pharmacology and dosing are described in US 8,039,456 B2/US 8,039,457 B2 (examples detailing GI models, acute deaths at 10 mg/kg IV, and non‑monotonic efficacy across 0.01–2.5 mg/kg).
• Phase II clinical trial registries: NCT00672074 (COMPLETED) and NCT01280344 (COMPLETED) list safety/tolerability as outcomes and define dose regimens of 0.03–0.06 mg/kg BID/TID; detailed AE results were not present in the accessed registry summaries (NCT00672074, NCT01280344).

Available sources document an acute lethality signal at 10 mg/kg IV in rats, non‑monotonic GI pharmacodynamic responses over 0.01–2.5 mg/kg IV, and short‑term human tolerability at 0.01–0.06 mg/kg IV with pharmacodynamic activity. Formal LD50 values, organ‑specific toxicology, and genotoxicity testing results were not reported in the retrieved texts and remain to be established from dedicated toxicology reports or peer‑reviewed studies.

Evidence Gaps#

• Human adverse event data is limited to anecdotal reports
• Systematic adverse event monitoring has not been conducted
• Drug interaction studies are incomplete
• Long-term safety profiles are unknown

Related Reading#

• Ipamorelin overview and research guide
• Ipamorelin dosing protocols
• Ipamorelin risks and legal status