Ipamorelin side effects and results in studies
In the one placebo-controlled human trial, adverse events were reported in 87.5% of patients given ipamorelin and 94.8% given placebo, and the authors described it as well tolerated. The abstract does not list individual events, and the trial found no significant efficacy difference from placebo.
What are the side effects of ipamorelin? The only controlled human safety data in our records come from a phase 2 trial in 114 adults recovering from bowel resection (Beck et al. 2014). Treatment-emergent adverse events were reported in 87.5% of the ipamorelin group and 94.8% of the placebo group. The abstract does not name individual events or give their rates, so this page does not list any. The authors concluded that 0.03 mg/kg twice daily for up to 7 days was well tolerated.
Those percentages look high because the patients had just had abdominal surgery, and most post-surgical patients have some adverse event whatever they are given. The meaningful comparison is between the two groups, and the rate was not higher with ipamorelin.
Does ipamorelin raise cortisol? In the study that first characterised it, ipamorelin did not raise ACTH or cortisol in swine above the levels seen after GHRH, even at doses more than 200 times the dose for half its growth hormone effect (Raun et al. 1998). GHRP-6 and GHRP-2 did raise both. Ipamorelin also left FSH, LH, prolactin and TSH unchanged. This selectivity was measured in animals, not in people.
What results did the studies measure? In healthy men, a single infusion produced one pulse of growth hormone that peaked at about 40 minutes (0.67 hours) and returned to negligible levels (Gobburu et al. 1999). In rats, ipamorelin sped up gastric emptying and bowel movement after abdominal surgery, and increased longitudinal bone growth, bone mineral content and body weight. In rats also given a glucocorticoid, it preserved muscle strength and bone formation.
The rat bone results need care. Svensson et al. found that bone mineral content rose because the bones grew larger, while bone density itself was unchanged. Johansen et al. saw faster bone growth without any change in total IGF-I or serum bone-turnover markers. None of these outcomes has been measured in people.
Adverse events reported
| Event | As reported | Source |
|---|---|---|
| Any treatment-emergent adverse event | 87.5% with ipamorelin vs 94.8% with placebo in post-surgical patients; individual events not listed in the abstract; described as well tolerated | Beck DE et al. |
| ACTH and cortisol release (swine) | Not raised above GHRH levels, even at more than 200-fold the ED50; GHRP-6 and GHRP-2 raised both | Raun K et al. |
| FSH, LH, prolactin and TSH (swine) | Not affected | Raun K et al. |
| Pituitary GH response after 15 days of dosing (rat) | Plasma GH response to a provocative dose of ipamorelin marginally reduced (P < 0.03); pituitary GH content unchanged | Johansen PB et al. |
Outcomes measured
| Outcome | Result as reported | Source |
|---|---|---|
| Time to first tolerated solid meal after bowel surgery (human) | Median 25.3 h vs 32.6 h with placebo (p = 0.15, not significant) | Beck DE et al. |
| Growth hormone release after one infusion (human) | Single GH episode peaking at 0.67 h at all five doses; half-maximal stimulation at 214 nmol/L | Gobburu JV et al. |
| Gastric emptying after abdominal surgery (rat) | 52% of the meal left in the stomach vs 78% with vehicle (P < 0.05) | Greenwood-Van Meerveld B et al. |
| Colonic transit and food intake after surgery (rat) | Single 1 mg/kg dose shortened time to first bowel movement; repeated dosing raised faecal output, food intake and weight gain | Venkova K et al. |
| Longitudinal bone growth (rat) | 42 micrometres/day with vehicle vs 44, 50 and 52 micrometres/day across three doses (P < 0.0001) | Johansen PB et al. |
| Bone mineral content (rat) | Increased with body weight; density and mineral concentration unchanged | Svensson J et al. |
| Muscle strength and bone formation with a glucocorticoid (rat) | Calf muscle tetanic tension significantly higher; periosteal bone formation rate four-fold higher than glucocorticoid alone | Andersen NB et al. |
| Weight loss during cisplatin treatment (ferret) | Reduced by about 24% in the delayed phase (48–72 h); no effect on emesis | PMID 39043357 |
What the studies don't show
The human safety data come from one small, short trial in post-surgical patients, with no list of specific events in the abstract. There are no human data on repeated use over weeks or months, and the bone, muscle and body-weight results are from rodents. No study here tested ipamorelin combined with CJC-1295.