Side-by-side comparison of mechanisms, dosing, interactions, and stacking potential.
| Ipamorelin | P21 (Cerebrolysin Analog) | |
|---|---|---|
| Category | Peptides | Peptides |
| Standard Dose | Research indicates 200-300 mcg administered 1-3 times daily via subcutaneous injection. | Research indicates 750 mcg-1 mg daily via intranasal administration or subcutaneous injection. |
| Timing | Best administered at bedtime for synergy with natural GH peak. Also effective upon waking and post-workout. Always on empty stomach. | Morning dosing preferred for cognitive effects. |
| Cycle Duration | 12-24 week cycles with 4-8 week breaks. | 4-8 week cycles with 4-week rest periods. |
| Evidence Level | moderate_human | animal_plus_anecdotal |
Ipamorelin is a pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH2) that acts as the first selective growth hormone secretagogue receptor (GHS-R1a/ghrelin receptor) agonist. Unlike other GHRPs, it selectively stimulates GH release without significantly affecting ACTH, cortisol, prolactin, or aldosterone — even at doses 200-fold above the ED50 for GH release. This selectivity profile is comparable to GHRH itself but operates through the distinct ghrelin receptor on pituitary somatotrophs.
Research indicates 200-300 mcg administered 1-3 times daily via subcutaneous injection.
Best administered at bedtime for synergy with natural GH peak. Also effective upon waking and post-workout. Always on empty stomach.
12-24 week cycles with 4-8 week breaks.
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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