Comparison
Ipamorelin vs Thymosin Alpha-1
Side-by-side of Ipamorelin and Thymosin Alpha-1. Every row below is pulled from the compound schema and will update as our data grows. For deeper reads, follow through to each compound page.
Ipamorelin
Ipamorelin peptide benefits: selective ghrelin-receptor GHRP, 200 to 300 mcg dosage, GH pulse without cortisol or prolactin rise, CJC-1295 stack vs sermorelin.
Thymosin Alpha-1
Thymosin alpha-1 peptide (Zadaxin, thymalfasin): 28-amino-acid TA1 immunomodulator. Dosing, T-cell effects, hepatitis B and HCV adjunct evidence.
Effects at a glance
Ipamorelin
- •Pentapeptide GHS-R1a agonist with the cleanest selectivity profile in the GHRP class
- •Minimal cortisol and prolactin elevation at standard doses (substantially less than GHRP-2 or hexarelin)
- •~2 hour plasma half-life, longest of the synthetic GHRPs
- •Largest human safety database (~600 participants in Helsinn's postoperative ileus phase 2)
- •Standard pairing for CJC-1295 no-DAC at 200 to 300 mcg subcutaneously 2 to 3 times daily
- •Banned by WADA under S2; never reached registration despite phase 2b development
Thymosin Alpha-1
- •28-amino-acid synthetic peptide identical to thymic-derived immunomodulator
- •Approved in over 35 countries as Zadaxin for hepatitis B, hepatitis C adjunct, and immune support
- •Not FDA approved in US; compounded by 503A/503B pharmacies for off-label immune support
- •Modulates T-cell maturation, NK activity, and Th1 polarization in immunocompromised states
- •Standard label dose: 1.6 mg subcutaneously twice weekly
- •Cleanest safety profile in the peptide class with hundreds of regulated trials behind it
Side-by-side
| Attribute | Ipamorelin | Thymosin Alpha-1 |
|---|---|---|
| Category | peptide | peptide |
| Also known as | NNC 26-0161, Aib-His-D-2-Nal-D-Phe-Lys-NH2 | Talpha1, Ta1, Zadaxin, Thymalfasin |
| Half-life (hr) ↗ | 2 | 2 |
| Typical dose (mg) ↗ | 0.2 | 1.6 |
| Dosing frequency | 2-3x daily | 2x weekly |
| Routes | subcutaneous, intravenous | subcutaneous, intramuscular |
| Onset (hr) | 0.25 | 24 |
| Peak (hr) | 1 | 168 |
| Molecular weight | 711.86 | 3108.32 |
| Molecular formula | C38H49N9O5 | C129H215N33O55 |
| Mechanism | Selective GHS-R1a agonist that stimulates pulsatile GH release with minimal cortisol or prolactin co-activation. Suppresses hypothalamic somatostatin and stimulates pituitary somatotrophs. | Synthetic peptide modulator of innate and adaptive immunity. Promotes T-cell maturation and CD4/CD8 production, modulates Th1/Th2 balance, stimulates NK cell activity, and modulates TLR2/TLR9 signaling in dendritic cells. |
| Legal status | Not FDA approved; advanced through phase 2b in postoperative ileus before discontinuation; research-use-only grey market; banned by WADA | Approved in 35+ countries as Zadaxin (hepatitis B, hepatitis C adjunct, immune support); not FDA approved in US; compounded by 503A/503B pharmacies for off-label use; not on WADA Prohibited List |
| WADA status | banned | unknown |
| DEA / Rx | Not scheduled (research chemical) | Rx only via international approval or US compounding (no controlled-substance schedule) |
| Pregnancy | Insufficient data; not recommended | Not recommended; insufficient data |
| CAS | 170851-70-4 | 62304-98-7 |
| PubChem CID | 11338566 | 16130571 |
| Wikidata | Q1666741 | Q913854 |
Safety profile
Ipamorelin
Common side effects
- injection-site irritation
- vivid dreams
- transient mild head pressure
- occasional headache
Contraindications
- pregnancy
- active malignancy
- history of pituitary tumor
- uncontrolled diabetes
Interactions
- CJC-1295: synergistic GH release via parallel GHRH and ghrelin pathways; standard pairing(minor)
- sermorelin: additive GH release; functionally similar pairing to CJC-1295 with shorter GHRH half-life(minor)
- insulin: sustained GH can blunt insulin sensitivity over weeks(moderate)
- corticosteroids: blunt GH response; reduce expected efficacy(moderate)
Thymosin Alpha-1
Common side effects
- mild injection-site irritation (rare)
- transient mild fatigue (rare)
- occasional headache (rare)
Contraindications
- pregnancy
- lactation
- active organ transplant rejection therapy
- systemic immunosuppression for autoimmune disease (relative)
- severe active autoimmune disease (caution)
Interactions
- interferon-alpha: additive immune effect; used clinically in approved combination protocols(minor)
- calcineurin inhibitors (cyclosporine, tacrolimus): theoretical destabilization of immunosuppression; avoid(major)
- antimetabolites (azathioprine, mycophenolate): theoretical destabilization of immunosuppression; avoid(major)
- vaccine administration: may augment vaccine response in elderly or immunocompromised; coordinate with clinician(minor)
Which Should You Take?
Thymosin Alpha-1 comes out ahead for most readers on the criteria we weight: 3 catalogued goals, Approved in 35+ countries as Zadaxin (hepatitis B, hepatitis C adjunct, immune support); not FDA approved in US; compounded by 503A/503B pharmacies for off-label use; not on WADA Prohibited List, with a Tier-A outcome catalogued. Ipamorelin is the right call when one of the conditionals below applies.
- → If your priority is growth-hormone axis, pick Ipamorelin.
- → If your priority is body composition, pick Ipamorelin.
- → If your priority is immune support, pick Thymosin Alpha-1.
- → If your priority is antiviral action, pick Thymosin Alpha-1.
Default choice: Thymosin Alpha-1. Wider use case, a Tier-A evidence outcome catalogued, and broader goal coverage. Reach for Ipamorelin only if your priority sits squarely in the goals it owns above.
This verdict is generated from each compound's schema (goals, legal status, evidence outcomes, dosing route). It updates automatically as our compound data evolves; the deeper read sits on each individual compound page.
Common questions
What is the difference between Ipamorelin and Thymosin Alpha-1?
Ipamorelin and Thymosin Alpha-1 differ in category (peptide vs peptide), mechanism, and typical dosing. See the side-by-side table for full details.
Which has a longer half-life, Ipamorelin or Thymosin Alpha-1?
Ipamorelin half-life is 2 hours; Thymosin Alpha-1 half-life is 2 hours.
Can you stack Ipamorelin with Thymosin Alpha-1?
Stack compatibility depends on mechanism overlap, legal status, and individual response. Check each compound page for specific interactions and contraindications before combining.
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