This comparison is lopsided by construction. One side is an approved medicine with a label, a phase 3 programme and two meta-analyses published this year. The other is a research peptide whose single efficacy trial did not work and whose developer walked away. Setting them side by side is still useful — because it shows exactly what the evidence behind a growth-hormone peptide looks like when it exists, and how little of it exists for the one sold more often.
The amounts below are from the tesamorelin labels and published pharmacology studies, every one attributed and dated. They record the approved regimen for one patient group and what investigators infused — not what anyone else should use.
Two molecules, two receptors
- Tesamorelin is the full 44-amino-acid human growth-hormone-releasing hormone with a hexenoyl group attached at one end to slow its breakdown. It acts on the GHRH receptor.
- Ipamorelin is a synthetic pentapeptide that acts on the ghrelin receptor.
Both end in a pulse of growth hormone from the pituitary. They reach it by different routes — the same split described on ipamorelin vs sermorelin, where sermorelin plays the GHRH role that tesamorelin plays here.
One has a label
Tesamorelin was approved by FDA under BLA 022505 on 10 November 2010 as a new molecular entity. Its current labels (EGRIFTA SV and EGRIFTA WR, both updated July 2026 on openFDA) name one use only — excess belly fat in adults with HIV lipodystrophy.
The same section then fences the drug in, and each limit cuts against something said about it in gyms:
- Whether it is safe for the heart over years is unknown.
- Patients whose organ fat does not fall should have their treatment reviewed.
- It is not a weight-loss drug, because body weight stays flat.
- Nothing shows it helps people keep taking their HIV medicines.
The regimen on the labels. EGRIFTA SV: 1.4 mg once daily under the skin of the abdomen. EGRIFTA WR: 1.28 mg once daily. The labels state the two formulations "are not substitutable". The original EGRIFTA used 2 mg.
Ipamorelin has no label. No regulator has ever approved it, and FDA's compounding lists place it in category 2, the group flagged on safety grounds.
One has a body-composition number
Two independent meta-analyses published in 2026 pooled tesamorelin's randomised trials in HIV-associated lipodystrophy. They report the same lean-body-mass increase: 1.42 kg. One of them pooled four trials involving 909 people. Visceral fat fell substantially in both analyses.
That figure has three limits that matter to anyone reading it as a muscle claim:
- The population. Every trial enrolled people with HIV and abdominal fat accumulation — a group defined by a disease and a drug side effect, not by training status.
- The endpoint. Lean body mass measured by imaging includes water and organ tissue as well as muscle. Neither meta-analysis reports a strength or physical-function outcome.
- The band. The other trial-tested compounds on this axis, MK-677 and capromorelin, land in the same place — a kilogram or so of lean tissue over months, and no strength gain measured in any of the three. The MK-677 and growth hormone secretagogues pages set out that ceiling.
The functional question is finally being asked: NCT06554717 combines the drug with an exercise programme in people with HIV and measures physical function. On 2026-09-28 it was recruiting toward 100 people, with results not due before June 2028.
Ipamorelin has no body-composition number because no trial has measured one. Its one published efficacy trial measured how quickly 117 patients' bowels recovered after surgery. The drug arm was faster by about seven hours on the median, but at p = 0.15 that gap was not distinguishable from chance, and no secondary endpoint separated either. A 320-patient follow-on completed in 2013 and never posted results.
What the approved drug's label warns about
This is the part of the comparison that is easiest to misread. Tesamorelin has a long warnings section; ipamorelin has none. That is not because ipamorelin is safer — it is because nobody has run the trials that would fill one in.
The tesamorelin label's warnings and precautions:
- Increased risk of neoplasms — any pre-existing malignancy should be inactive and its treatment complete before starting, and the drug stopped on any sign of recurrence.
- Elevated IGF-1 — the effects of prolonged elevation "are unknown"; IGF-1 is to be monitored and discontinuation considered if it stays high.
- Fluid retention, which may include oedema, joint pain and carpal tunnel syndrome.
- Glucose intolerance or diabetes.
- Hypersensitivity and injection-site reactions.
Reactions reported in more than 5% of trial patients: joint pain, injection-site redness and itching, pain in the limbs, peripheral swelling and muscle pain.
Every one of those follows from raising growth hormone and IGF-1. None of them has been looked for systematically with ipamorelin, which raises growth hormone too. How this class compares with anabolic steroids on side effects and on detection is set out on peptides vs steroids and peptides and drug testing.
Half-life, the one number that favours ipamorelin
| Tesamorelin | Ipamorelin | |
|---|---|---|
| Elimination half-life | 8 minutes (EGRIFTA SV, healthy subjects, single 1.4 mg dose) | about 2 hours (healthy men, IV infusion; Gobburu 1999) |
| Absolute bioavailability under the skin | below 4% (2 mg dose, healthy adults) | not published for subcutaneous use |
| Growth-hormone response | pulsatile | a single pulse peaking at 0.67 h at every dose tested |
Ipamorelin lingers longer, and marketing copy sometimes treats that as an advantage. It is a pharmacokinetic fact about the molecule, not a clinical one: the drug with the 8-minute half-life is the one with a measured body-composition effect, because it is the one that was tested.
The evidence, counted
| Count, 2026-09-28 | Tesamorelin | Ipamorelin |
|---|---|---|
| PubMed records | 121 | 54 |
| Tagged as randomised trials | 21 | 2 |
| ClinicalTrials.gov registrations | 24 | 3 |
| Pooled trials with a lean-mass result | 4 trials, 909 people | 0 |
| Trials in trained healthy adults | 0 | 0 |
| Papers naming both compounds | 6 — all reviews |
No study has ever given both. The six papers that mention them together are reviews of peptides in sports medicine, orthopaedics, doping and ageing.
In sport
Both are prohibited at all times under section S2 of the WADA Prohibited List. Tesamorelin's approval does not change that for a tested athlete without a therapeutic use exemption, and the label itself calls it a growth-hormone-releasing factor analogue. The compound table is on WADA status by compound.
What is established, and what is not
- Established: tesamorelin is an approved drug with a narrow indication, pooled randomised evidence of a 1.42 kg lean-mass gain in people with HIV lipodystrophy, and a label that warns about tumours, IGF-1, fluid, glucose and unknown long-term cardiovascular safety.
- Established: ipamorelin has never been approved and has no body-composition data; its one efficacy trial did not separate from placebo.
- Not established: that tesamorelin improves strength or performance in anyone, or builds muscle in trained adults.
- Not established: anything about ipamorelin and muscle — the question has never been tested.
Sources
- EGRIFTA SV and EGRIFTA WR (tesamorelin) prescribing information, sections 1, 2, 5, 6 and 12.3, via openFDA, effective 2026-07-29, read 2026-09-28.
- FDA, Drugs@FDA via openFDA: BLA 022505, original approval 2010-11-10.
- Meta-analyses: Badran AS, Helal A, et al. Body composition, hepatic fat, metabolic, and safety outcomes of tesamorelin … in HIV-associated lipodystrophy. Obes Res Clin Pract 2026;20(1):2–12. PMID 41545261 · Ditta AM, Naeem RM, et al. Efficacy and safety of tesamorelin in people living with HIV with lipodystrophy: a systematic review and meta-analysis. J Int Assoc Provid AIDS Care 2026;25. PMID 42538058
- Beck DE, et al. Prospective, randomized, controlled, proof-of-concept study of the ghrelin mimetic ipamorelin for the management of postoperative ileus in bowel resection patients. Int J Colorectal Dis 2014. PMID 25331030
- Gobburu JV, Agersø H, Jusko WJ, Ynddal L. Pharmacokinetic-pharmacodynamic modeling of ipamorelin, a growth hormone releasing peptide, in human volunteers. Pharm Res 1999;16(9):1412–1416. PMID 10496658
- ClinicalTrials.gov: NCT06554717, status read 2026-09-28; intervention searches for tesamorelin (24) and ipamorelin (3).
- PubMed searches, 2026-09-28:
tesamorelin121;ipamorelin54;ipamorelin AND tesamorelin6, all publication type Review. - WADA Prohibited List, section S2.