Dihexa 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.
Dihexa
Dihexa is a synthetic hexapeptide derived from angiotensin IV, developed at Washington State University. It is considered one of the most potent nootropic peptides known — in rodent models it outperforms BDNF itself for synaptogenesis and cognitive enhancement, acting through the hepatocyte growth factor (HGF) / c-Met receptor system. Unlike most nootropics, Dihexa is highly lipophilic and can be administered transdermally or orally.
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| Dihexa | Leucine Enkephalin (Leu-Enkephalin) | |
|---|---|---|
| Category | Nootropic & Cognitive | Nootropic & Cognitive |
| Also known as | PNB-0408, N-hexanoic-Tyr-Ile-(6) aminohexanoic amide | Leu5-enkephalin, YGGFL, L-enkephalin, endogenous opioid pentapeptide |
| Evidence | Preclinical only | Research-stage |
| Dosing range | 10mg–20mg mg, Once daily (or every other day — long-lasting effects) | 0.1mg–1mg mg, Intranasal or SC; extremely short half-life requires frequent dosing or continuous delivery |
| Administration | Oral (capsule), Transdermal (cream/lotion — lipophilicity makes this effective), Subcutaneous injection (less common) | Intranasal, Subcutaneous injection, Intraventricular (research only) |
| Key side effects | Potential for pro-proliferative effects — HGF/c-Met pathway promotes cell growth (theoretical cancer concern at high doses), Headache (uncommon), Mental fatigue if overdosed, Long half-life means effects accumulate — take every other day initially | 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
- Evidence level differs: Dihexa is preclinical only, while Leucine Enkephalin (Leu-Enkephalin) is research-stage.
- Administration: Dihexa — Oral (capsule), Transdermal (cream/lotion — lipophilicity makes this effective), Subcutaneous injection (less common); Leucine Enkephalin (Leu-Enkephalin) — Intranasal, Subcutaneous injection, Intraventricular (research only).
- Frequency: Dihexa is typically Once daily (or every other day — long-lasting effects); Leucine Enkephalin (Leu-Enkephalin) is Intranasal or SC; extremely short half-life requires frequent dosing or continuous delivery.
How each works
Dihexa
Dihexa (PNB-0408) was developed by Joseph Harding and colleagues at WSU as a metabolically stable angiotensin IV analog. It binds hepatocyte growth factor (HGF), potentiating its interaction with the c-Met receptor — a pathway critical for dendritic branching, synapse formation, and synaptic plasticity. In rodent Alzheimer's and scopolamine-impaired models, Dihexa restored cognitive performance at doses ~7 orders of magnitude lower than BDNF. It readily crosses the blood-brain barrier due to its lipophilicity, unlike BDNF itself.
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.