Ipamorelin Side Effects: Severity Distribution by Patient Phenotype

Does ipamorelin severity differ by patient phenotype?

The adverse-event figures below come from one group of patients: adults recovering from bowel resection who received intravenous ipamorelin. No published study reports those rates by patient phenotype, and FDA found no human pharmacokinetic, safety or efficacy data for subcutaneous ipamorelin [1].

What the bowel-surgery trial recorded

Beck and colleagues ran a multicentre, randomised, double-blind, placebo-controlled phase 2 trial of ipamorelin for postoperative ileus. It enrolled 117 adults having small or large bowel resection, of whom 114 were analysed, with 0.03 mg/kg intravenously twice daily from postoperative day 1 to day 7 or discharge [2].

Any treatment-emergent adverse event occurred in 87.5% of the ipamorelin group and 94.8% of the placebo group [2]. The trial did not meet its main efficacy endpoint: median time to first tolerated solid meal was 25.3 hours with ipamorelin and 32.6 hours with placebo (p=0.15) [2].

FDA's summary of the trial lists these adverse events: low potassium in 12.5% versus 3.4%, insomnia in 10.7% versus 5.2%, high blood sugar at discharge in 14.3% versus 8.6%, and serious adverse events in 17.9% versus 15.5% [1]. Two ipamorelin-treated patients died of surgical complications (bowel surgery for colon cancer with an anastomotic leak); FDA said it is unclear whether the deaths were related to ipamorelin, but that they raise safety concerns [1].

What FDA expects from the growth hormone axis

Ipamorelin is a five-amino-acid peptide that releases growth hormone by acting at the ghrelin/GH-secretagogue receptor rather than the GHRH receptor [5]. Because it stimulates the GH and IGF-1 axis, FDA's reviewers said it may carry the risks listed on approved growth hormone labels: neoplasm, glucose intolerance and diabetes, intracranial hypertension, fluid retention, hypothyroidism and pancreatitis, and possibly QT prolongation as seen with the approved GH stimulator macimorelin. FDA found no data showing it would not [1].

Blood sugar and potassium

Two laboratory-related findings stand out in the trial. High blood sugar at discharge occurred in 14.3% of ipamorelin patients versus 8.6% on placebo, and low potassium in 12.5% versus 3.4% [1]. Both figures describe the trial population as a whole. FDA separately lists glucose intolerance and diabetes among the possible risks of drugs acting on the GH and IGF-1 axis [1]. The patients were postoperative and received intravenous dosing, so the trial does not give a general estimate for other settings.

What the compounded product adds

FDA's concerns about compounded ipamorelin are about the product itself: possible immunogenicity for certain routes because of aggregation and impurities, unnatural amino acids that complicate characterisation, and a published study that identified serious adverse events including death when ipamorelin was given intravenously to improve gastric motility [4]. Ipamorelin acetate sits in category 2, FDA's list of bulk substances that may present significant safety risks, for outsourcing facilities, where it has remained since September 29, 2023 [4][6]. For state-licensed pharmacies it appears in the withdrawn-nominations table and in none of the three current categories [4][7].