Pentapeptide-18 vs Acetyl Hexapeptide-8: Leuphasyl or Argireline

Pentapeptide-18 and Acetyl Hexapeptide-8 both target the look of expression lines, but they act at two different points of the same nerve-to-muscle signal, so the real answer to pentapeptide-18 vs acetyl hexapeptide-8 is that they are partners more than rivals. In the manufacturer's 28-day eye-area test, a cream with 5% Argireline-type solution gave a 16.26% average drop in wrinkle depth, 5% Leuphasyl-type solution gave 11.64%, and the two together gave 24.62%.

Most pages that compare them stop at that headline. Below we look at what each peptide is on paper, why their mechanisms add up rather than overlap, how the solution and powder grades are dosed, and how to put them in one bottle without wasting either.

Two Peptides, Two Identities

Acetyl Hexapeptide-8, the Argireline Peptide

Acetyl Hexapeptide-8 is a six-amino-acid peptide with the sequence Ac-Glu-Glu-Met-Gln-Arg-Arg-NH2 and CAS number 616204-22-9. Lipotec, now part of Lubrizol, launched it as Argireline, and older papers and labels still call it Acetyl Hexapeptide-3, which is the same molecule under its earlier INCI name. The sequence copies the N-terminal end of SNAP-25, one of the proteins that nerve endings use to package and release acetylcholine. It is sold mainly as a 0.05% water solution, which is what our Acetyl Hexapeptide-8 Solution is, and as a neat Acetyl Hexapeptide-8 Powder for brands that weigh their own peptide.

Pentapeptide-18, the Leuphasyl Peptide

Pentapeptide-18 is a five-amino-acid peptide, Tyr-D-Ala-Gly-Phe-Leu, CAS 64963-01-5, modeled on enkephalins, the small signaling peptides the body uses to quiet nerve activity. The D-alanine in the second position is a classic swap that makes enkephalin-type peptides harder for enzymes to break down. Lipotec sells it as Leuphasyl Solution with the INCI Water, Glycerin, Pentapeptide-18 and a caprylyl glycol preservative, and the technical sheet states 0.5 g of peptide per liter, the same 0.05% strength as Argireline solution. Ours comes both as a colorless Pentapeptide-18 Solution with a supplied pH of 2.0 to 5.0 and as a dry Pentapeptide-18 Powder.

How Each One Works on Expression Lines

Inside the Nerve Ending

A facial muscle contracts when a nerve ending releases acetylcholine, and that release depends on the SNARE complex, a set of three proteins that docks the vesicle full of acetylcholine onto the cell membrane. Acetyl Hexapeptide-8 competes with SNAP-25 for its place in that complex. The complex still forms, but less firmly, so fewer vesicles release their contents. A 2025 review in Pharmaceuticals on acetyl hexapeptide-8 describes it exactly this way: it destabilizes the complex rather than breaking any of its parts, which is why the result is a softer contraction rather than a blocked one.

Before the Signal Starts

Pentapeptide-18 works one step earlier. Like natural enkephalins, it binds to enkephalin receptors on the outside of the nerve cell. Those receptors are coupled to G proteins, and their activation closes calcium channels, which lowers how excitable the neuron is. With less calcium coming in, fewer vesicles fuse and less acetylcholine leaves the nerve. Cosmetics and Toiletries summarized it as a modified enkephalin that modulates acetylcholine release by decreasing neuronal excitability, a mechanism independent of the SNARE complex.

Why the Mechanisms Add Up

Because one peptide turns down the trigger and the other loosens the release machinery, they do not compete for the same target. In Lipotec's neuron culture test, 1 mM of Argireline cut glutamate release by about 20%, 1 mM of Leuphasyl by about 11%, and the two together by about 40%, which the company described as a synergistic effect. That in vitro result is the reason most expression-line serums that use Pentapeptide-18 also contain Acetyl Hexapeptide-8.

What the Published Data Shows

Manufacturer Studies

The best-known numbers come from three parallel 28-day tests in Lipotec's Leuphasyl dossier, each with 14 or 15 volunteers aged 39 to 64 applying a cream twice a day around the eyes and measured with silicone replicas. The Argireline cream averaged 16.26% less wrinkle depth with individual results up to 31.80%, the Leuphasyl cream averaged 11.64% with a best result of 23.55%, and the combination averaged 24.62% with a best result of 46.53%. Separately, the original Argireline paper by Blanes-Mira and colleagues in the International Journal of Cosmetic Science in 2002 reported up to 30% less wrinkle depth after 30 days with a 10% solution in an oil-in-water emulsion.

Independent and Review Data

Acetyl Hexapeptide-8 has the larger body of work, including permeation studies, randomized trials and formulation research on getting it through the skin barrier, all summarized in the 2025 review. Pentapeptide-18 has far fewer studies. An open-label study by Dragomirescu and colleagues in 2014 with 20 volunteers over 60 days used it with other actives and reported smoother-looking forehead and eye-area lines, but it was not placebo-controlled. The honest reading is that Acetyl Hexapeptide-8 is the stronger stand-alone ingredient on current evidence, and Pentapeptide-18 earns its place as a booster next to it.

Pentapeptide-18 vs Acetyl Hexapeptide-8 in Formulation

Dosing the Solutions

Lipotec recommends 3 to 10% of Leuphasyl Solution and 2 to 10% of Argireline solution in the finished product. Since both carry 0.05% peptide, 5% of either solution puts about 25 ppm of peptide into the formula, which is the level used in the 28-day tests. A common starting point for a dual serum is 5% of each solution, copying the combination that was tested, and then moving one of them up toward 10% if the budget and stability results allow it.

Dosing the Powders

Neat powders let you build a more concentrated serum or make your own stock, and our cards ask you to follow the dose on each lot's certificate of analysis because peptide content, purity and the acetate counter-ion vary by lot. The math is simple: to match 5% of a 0.05% solution, you need 25 mg of active peptide per kilogram of finished product. Weighing that directly is error-prone, so dissolve a larger amount in distilled water as a stock and dose the stock. Our cosmetic peptide powders guide walks through milligram weighing, stock solutions and storage.

Phase, Temperature and pH

Both peptides are water-soluble and belong in the water phase at the end of the process. Lipotec's sheets ask for addition below 40 °C, and for an emulsion, after the emulsion has formed. The Argireline sheet gives a working pH range of 3.0 to 8.0 and lists oxidants, electrophiles and tannins as incompatibilities, so keep peroxides, strong oxidizing antioxidants at high doses and tannin-rich botanical extracts away from the peptide phase. A finished serum between pH 5 and 6.5 suits both peptides and most skin-feel goals. Add each solution separately, stir gently, and check clarity and pH after each one.

Building a Serum With Both

A Simple Dual-Peptide Frame

For a 100 g test batch, a light gel serum might use water to balance, 3 to 5% glycerin, a hydrated gum or a hyaluronic acid solution for slip, a broad-spectrum preservative at its supplier's level, and then 5 g of Acetyl Hexapeptide-8 Solution plus 5 g of Pentapeptide-18 Solution in the cool-down. Adjust the pH at the end and record it. Use these numbers as a starting frame for your own stability and preservative challenge testing, not as a finished product.

Adding a Third Expression-Line Peptide

Some brands extend the idea with Acetyl Octapeptide-3, the eight-amino-acid relative of Acetyl Hexapeptide-8 known as SNAP-8, which acts on the same SNARE target. Our Acetyl Octapeptide-3 Solution fits the same cool-down step. Because it shares Argireline's mechanism, it tends to overlap with Acetyl Hexapeptide-8 rather than add a new route, while Pentapeptide-18 is the one that brings a different mechanism to the blend. For a broader recipe that pairs these with collagen-supporting peptides, see our peptide serum recipe for wrinkles.

Packaging and Storage

Peptide serums keep best in airless pumps or opaque droppers, away from heat and light. Before launch, run a four-week check at room temperature, at 40 °C and in the fridge, watching clarity, odor and pH. Keep the raw solutions closed and refrigerated. The Leuphasyl sheet notes that cold storage can occasionally make the preservative precipitate, which does not affect the peptide, so warm the drum gently to room temperature and mix before weighing.

Which One Should You Choose

If a formula can carry only one expression-line peptide, Acetyl Hexapeptide-8 is the stronger choice on the published data, and it is also the name more shoppers recognize on an ingredient list. If the budget allows two, add Pentapeptide-18 rather than a second SNARE peptide, since its separate mechanism is where the combined result in the manufacturer test came from. Pentapeptide-18 on its own makes sense mostly for brands that want to avoid a very common ingredient or tell a different story on the label.

Keep the claims cosmetic. Copy such as smoother-looking forehead lines, softer-looking crow's feet and a more relaxed-looking expression is appropriate, while comparing a serum to injections, promising that it stops muscle movement or saying it changes how nerves work moves the product out of cosmetics in the US. Both peptides, and their relatives, are in our peptide solutions section and our peptide powders section.

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