Leucine Enkephalin (Leu-Enkephalin) vs Noopept
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.
Leucine 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 profileNoopept
Dipeptide-derived nootropic developed in Russia and used across Eastern Europe as a cognitive enhancer and neuroprotective agent. Structurally related to piracetam but estimated to be approximately 1000× more potent by weight. Rapidly crosses the blood-brain barrier and is hydrolyzed to the endogenous neuropeptide cycloprolylglycine, which is proposed as its primary active metabolite.
Full profile| Leucine Enkephalin (Leu-Enkephalin) | Noopept | |
|---|---|---|
| Category | Nootropic & Cognitive | Nootropic & Cognitive |
| Also known as | Leu5-enkephalin, YGGFL, L-enkephalin, endogenous opioid pentapeptide | GVS-111, N-phenylacetyl-L-prolylglycine ethyl ester, omberacetam, N-Phenylacetyl-L-Prolylglycine Ethyl Ester |
| Evidence | Research-stage | Research-stage |
| Dosing range | 0.1mg–1mg mg, Intranasal or SC; extremely short half-life requires frequent dosing or continuous delivery | 5mg–20mg mg, 1–3x daily oral or sublingual (8–12 week cycles) |
| Administration | Intranasal, Subcutaneous injection, Intraventricular (research only) | Oral (capsule/powder), Sublingual (dissolved under tongue), Intranasal |
| Key side effects | 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) | Headache (especially without choline supplementation), Irritability, Brain fog at high doses, Insomnia (if taken too late in day) |
| Cited sources | 2 references | 2 references |
Key differences
- Administration: Leucine Enkephalin (Leu-Enkephalin) — Intranasal, Subcutaneous injection, Intraventricular (research only); Noopept — Oral (capsule/powder), Sublingual (dissolved under tongue), Intranasal.
- Frequency: Leucine Enkephalin (Leu-Enkephalin) is typically Intranasal or SC; extremely short half-life requires frequent dosing or continuous delivery; Noopept is 1–3x daily oral or sublingual (8–12 week cycles).
How each works
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.
Noopept
Noopept (GVS-111) enhances AMPA-receptor function and increases expression of BDNF and NGF in the hippocampus and basal forebrain. Its active metabolite cycloprolylglycine acts as an endogenous neuropeptide with anxiolytic and cognition-enhancing properties. Russian clinical trials demonstrate cognitive improvement in subjects with cognitive impairment, with a better tolerability profile than piracetam at equipotent doses.
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.