Cortexin vs Leucine Enkephalin (Leu-Enkephalin)
A neutral, side-by-side comparison of two nootropic & cognitive peptides — their mechanisms, dosing ranges, administration routes, side effects, and research evidence. For research and educational purposes only.
Cortexin
Polypeptide nootropic extracted from the cortex of cattle or pigs, containing a mixture of low-molecular-weight neuropeptides (≤10 kDa). Registered pharmaceutical in Russia and widely used in Eastern European clinical medicine for stroke recovery, traumatic brain injury, cognitive decline, epilepsy, and cerebrovascular disease. Decades of Russian clinical literature support neuroprotective and neurorestorative effects.
Full profileLeucine Enkephalin (Leu-Enkephalin)
One of the two primary endogenous enkephalins, alongside met-enkephalin. This pentapeptide (Tyr-Gly-Gly-Phe-Leu) acts primarily on δ-opioid receptors and secondarily on μ-opioid receptors. Research interests span pain modulation, neuroprotection, mood regulation, and immune system modulation. Extremely short half-life in vivo due to rapid enkephalinase degradation.
Full profile| Cortexin | Leucine Enkephalin (Leu-Enkephalin) | |
|---|---|---|
| Category | Nootropic & Cognitive | Nootropic & Cognitive |
| Also known as | cortexin polypeptide, cortexin-10, neuropeptide bioregulator, cortexin-5 | Leu5-enkephalin, YGGFL, L-enkephalin, endogenous opioid pentapeptide |
| Evidence | Research-stage | Research-stage |
| Dosing range | 5mg–20mg mg, daily IM injection for 10-day courses | 0.1mg–1mg mg, Intranasal or SC; extremely short half-life requires frequent dosing or continuous delivery |
| Administration | Intramuscular injection | Intranasal, Subcutaneous injection, Intraventricular (research only) |
| Key side effects | Injection site pain, Rare allergic reaction, Headache (transient), Mild dizziness | Tolerance development with repeated use (opioid receptor class effect), Mild euphoria (δ-opioid mediated), Nausea (at high doses), Constipation (opioid class effect at high doses) |
| Cited sources | 2 references | 2 references |
Key differences
- Administration: Cortexin — Intramuscular injection; Leucine Enkephalin (Leu-Enkephalin) — Intranasal, Subcutaneous injection, Intraventricular (research only).
- Frequency: Cortexin is typically daily IM injection for 10-day courses; Leucine Enkephalin (Leu-Enkephalin) is Intranasal or SC; extremely short half-life requires frequent dosing or continuous delivery.
How each works
Cortexin
Cortexin's multi-component neuropeptide mixture modulates neurotransmitter systems, improves cerebral blood flow, enhances neuroplasticity (BDNF upregulation), and exhibits antioxidant and anti-apoptotic activity in neuronal tissue. Russian stroke rehabilitation trials show improved neurological deficit scores and functional recovery with 10-day cortexin courses compared to standard care alone. The mechanism involves multiple parallel neuropeptide signaling pathways.
Leucine Enkephalin (Leu-Enkephalin)
Leu-enkephalin was one of the first endogenous opioid peptides characterized, following the discovery of opioid receptors in 1973. It preferentially activates δ-opioid receptors (DOR) over μ-opioid receptors (MOR), producing analgesia, modulation of GABA release, and reward pathway activation. Enkephalinase (neprilysin/NEP, CD10) cleaves the Gly-Phe bond within ~2 minutes IV, necessitating stable analogues or NEP inhibitors for research applications.
This comparison aggregates public research and structured profile data for informational purposes only. It is not medical advice and does not recommend either compound for human use. Consult a qualified healthcare provider before considering any peptide.