What the trials recorded
The FDA pooled the CJC-1295 DAC volunteer studies for its December 2024 review, and the numbers are higher than the “well tolerated” line in the abstracts suggests. In the first trial, adverse events occurred in 33 of 35 people on the drug against two of seven on placebo: injection-site reactions in about 70%, transient hives in nearly 30%, headache in 63% against 14% on placebo, diarrhoea in 43% and in everyone at the highest dose, and flushing with a transient drop in blood pressure in around 30%. The pulsatility study recorded a dose-dependent rise in heart rate. Increased heart rate and systemic vasodilatory reaction are the two effects the FDA named when it put CJC-1295 in Category 2.
Ipamorelin’s record is thinner and gentler. A single intravenous dose in healthy men produced nothing notable. In the ileus trial, people on ipamorelin had more low potassium (12.5% vs 3.4%), insomnia (10.7% vs 5.2%), and high glucose at discharge (14.3% vs 8.6%) than people on placebo.
What the community reports
Hunger, above everything. Ipamorelin is a ghrelin mimetic and ghrelin is the hunger hormone, so a wave of appetite twenty minutes after the injection is the pharmacology working as designed. After that: water retention and puffy hands, tingling fingers, headache, sleepiness after the dose, vivid dreams, and injection-site redness. None of it has been quantified in a study.
The two trials that ended in deaths
CJC-1295’s only trial in patients was a Phase 2 study in HIV-associated visceral obesity. On July 13, 2006, about two hours after his eleventh weekly dose, a participant in Argentina reported chest discomfort, an ECG confirmed a heart attack, and he died within the hour. The attending physician put it down to pre-existing, silent coronary artery disease and judged it unrelated to the drug. ConjuChem stopped the trial on July 17, 2006, the data were never published, and the compound has not been in development since.
In ipamorelin’s 117-patient ileus trial, two people in the ipamorelin group died. Both had had bowel resections for colon cancer and developed anastomotic leaks, a known surgical complication. The FDA’s 2024 review said it was “unclear whether the two deaths were related to ipamorelin” but that their occurrence “raises safety concerns about the use of ipamorelin in compounding”.
Two readings are both correct. Neither death is evidence that the drug killed anyone. And both are the reason the safety record is so thin, because in each case the trial that could have told us more is the trial that stopped.
The mechanistic concerns
Blood glucose. Growth hormone opposes insulin. The FDA flagged glucose intolerance as a class concern for anything that stimulates GH release, the ileus trial saw more hyperglycaemia on ipamorelin, and the year-long MK-677 trial measured a rise in fasting glucose and a fall in insulin sensitivity.
IGF-1 and cancer. IGF-1 is a growth factor, every GH-axis drug carries a theoretical concern about feeding an existing tumour, and every approved one is contraindicated in active malignancy. For these two compounds the concern is unaddressed in any species over any relevant timeframe.
The pituitary. A 2020 study in the Journal of Clinical Investigation, using a long-acting GHRH analogue that the FDA’s review identified as CJC-1295 DAC, found DNA damage in mouse growth-hormone cells in culture and, after eight weeks of injections, in the pituitaries of living mice, with enlargement of the gland. With no carcinogenicity studies, the FDA concluded, the potential for pituitary hyperplasia and tumours with long-term use is unknown.
Appetite and fat. The one controlled comparison of ipamorelin against growth hormone, in mice, found that ipamorelin increased body fat, leptin, and food intake while growth hormone decreased fat. That is not a paradox. It is a ghrelin mimetic doing what ghrelin does.
Conclusion
The compounds’ own side effects are mostly mild and mostly what more growth hormone feels like. The serious questions — glucose, IGF-1, and the pituitary — are the ones nobody has run the study to answer.