Leuphasyl (Pentapeptide-18)

Mechanism

Leuphasyl (pentapeptide-18, sequence Tyr-D-Ala-Gly-Phe-Leu) is structurally modelled on enkephalins — endogenous opioid peptides that modulate neurotransmitter release. It is proposed to interact with enkephalin receptors, modulating calcium channel activity and reducing calcium-dependent acetylcholine release at the neuromuscular junction. This produces a mild, reversible muscle-relaxing effect intended to reduce repetitive facial muscle contractions that contribute to expression lines. The mechanism is analogous to but far weaker than botulinum toxin. Independent verification of this mechanism in peer-reviewed literature is limited.

Evidence base

In Vitro Evidence

Manufacturer (Lipotec/Lubrizol) data reports that Leuphasyl reduced glutamate release in an in vitro neuronal cell model by ~39% at 0.05 mM.

Clinical Evidence

A manufacturer-sponsored study (n≈20) reported ~11.6% reduction in wrinkle depth after 28 days of twice-daily topical application. A combination study with Argireline reported up to 24% reduction.

Limitations

• Evidence is almost entirely manufacturer-sponsored
• Small sample sizes
• No independent peer-reviewed replication
• Skin penetration of topically applied peptides is poorly characterised

Evidence grade: Limited.

Protocols

Leuphasyl is discussed in cosmetic formulation at typical concentrations of 0.05% (500 ppm) in topical emulsions, applied twice daily. It is often combined with Argireline (0.05%) for proposed synergistic effects. There are no researched or approved protocols for injectable use. All information is for research and formulation reference only — no human consumption or medical use is implied.

UK legal status

Leuphasyl (pentapeptide-18) is legal for research and cosmetic formulation use in the UK. It is not a controlled substance and is not a POM. As a cosmetic ingredient, it falls under the UK Cosmetics Regulation (retained EU Regulation 1223/2009). It is not approved for injectable use; any injectable administration could constitute an unlicensed medicine subject to MHRA enforcement.

Vendor notes

Leuphasyl is primarily available through cosmetic ingredient suppliers rather than research peptide vendors. Purchasers should verify supplier quality, request certificates of analysis, and ensure UK cosmetic regulation compliance. No UK peptide vendors are currently verified for bulk Leuphasyl supply.