Side-by-side comparison of mechanisms, dosing, interactions, and stacking potential.
| Hexarelin | P21 (Cerebrolysin Analog) | |
|---|---|---|
| Category | Peptides | Peptides |
| Standard Dose | Research indicates 100-200 mcg administered 1-2 times daily via subcutaneous injection. | Research indicates 750 mcg-1 mg daily via intranasal administration or subcutaneous injection. |
| Timing | On empty stomach, bedtime preferred. Avoid prolonged continuous use due to rapid desensitization. | Morning dosing preferred for cognitive effects. |
| Cycle Duration | 4-8 week cycles maximum, then 4+ week break. Hexarelin desensitizes faster than other GHRPs. | 4-8 week cycles with 4-week rest periods. |
| Evidence Level | moderate_human | animal_plus_anecdotal |
Hexarelin (Examorelin) is a synthetic hexapeptide GHS-R1a agonist and the most potent synthetic GH secretagogue by peak GH release. It stimulates GH release through both pituitary ghrelin receptors and hypothalamic pathways, with mechanisms involving regulation of GHRH and somatostatin. Hexarelin also demonstrates significant cardiac benefits through activation of cardiac GHS-R1a receptors, protecting against ischemia-reperfusion injury and reducing cardiac fibrosis via the CD36 scavenger receptor pathway.
Research indicates 100-200 mcg administered 1-2 times daily via subcutaneous injection.
On empty stomach, bedtime preferred. Avoid prolonged continuous use due to rapid desensitization.
4-8 week cycles maximum, then 4+ week break. Hexarelin desensitizes faster than other GHRPs.
P21 is a tetrapeptide (DGGL — Asp-Gly-Gly-Leu) derived from the most active region of ciliary neurotrophic factor (CNTF, residues 148-151), identified through reverse engineering of Cerebrolysin. An adamantylated glycine enhances BBB permeability and metabolic stability. P21 works through LIF/STAT3 pathway inhibition, BDNF/TrkB/CREB signaling enhancement, and restoration of synaptic proteins (synaptophysin, synapsin I) and glutamate receptors. It promotes neurogenesis and maturation of newborn neurons in the dentate gyrus.
Research indicates 750 mcg-1 mg daily via intranasal administration or subcutaneous injection.
Morning dosing preferred for cognitive effects.
4-8 week cycles with 4-week rest periods.
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