Plate V · The dose register
GHK-Cu Research-Dose Context: Concentrations, Routes and Pharmacokinetics
The concentrations and routes at which GHK-Cu has been studied — picomolar in cell culture, percent-range topically, milligram-per-kilogram in rodents — set out as a research register, never as a human protocol.
How to read these numbers
This GHK-Cu research-dose context page records the concentrations and routes used in published studies. It is not a dosing guide. GHK-Cu has no FDA- or EMA-approved therapeutic indication by any route; topical Copper Tripeptide-1 is a legal cosmetic ingredient, while injectable or systemic use is unapproved and research-only [3]. Every figure below is reported as 'studied at X in [species or model],' the only honest framing for a compound with strong preclinical data and thin controlled-human evidence.
The spread of concentrations is wide because the routes are so different. In human fibroblast cultures the collagen-synthesis effect begins between 10^-12 and 10^-11 M and peaks near 10^-9 M [1] — picomolar to nanomolar. Topical cosmetic and clinical formulations sit at roughly 0.05% to 2% (w/w) in creams, serums and gels. Rodent systemic studies use milligram-per-kilogram doses by injection. None of these translate into a human protocol, and we do not offer one.
Concentrations and routes in the literature
The research register, by model: in-vitro fibroblast collagen synthesis at 10^-12 to 10^-9 M [1]; topical cosmetic and clinical formulations at about 0.05% to 2% (w/w); the human hair-loss RCT used a topical 5-ALA+GHK complex at 50-100 mg/mL [4]. Rodent systemic work spans intraperitoneal dosing in pulmonary and silicosis models, oral gavage in colitis models, and intranasal delivery in cognitive models, generally in the milligram-per-kilogram range [6].
Routes studied are broad: topical (cream, serum, liposome, nano-lipid carrier, ionic-liquid microemulsion, wound dressing and nanofiber), intraperitoneal, intranasal, oral gavage, intravenous/subcutaneous, and intradermal microneedle delivery [5][10][14]. The point of cataloguing them is not to recommend any one — it is to show how route-dependent the evidence is, and why a topical result and an injectable claim are not the same finding.
Half-life and pharmacokinetics
No rigorous human pharmacokinetic half-life for GHK-Cu has been published. The free tripeptide (340.38 Da) is rapidly cleared by plasma peptidases: a rat HPLC study documented rapid metabolism of GHK to the dipeptide histidyl-lysine after intravenous dosing [15]. Secondary literature cites a short systemic elimination half-life on the order of 1-2 hours, with the copper-chelated complex more stable than free GHK, but these figures are not validated human data.
Topical application behaves entirely differently. Rather than a fast systemic clearance, topical GHK-Cu forms a dermal copper depot — about 97 ug/cm^2 retained over 48 hours in human skin [5]. That depot is why topical effects are described over weeks: the skin holds the copper and releases it slowly, the opposite of the rapid plasma clearance seen after injection. The two pharmacokinetic pictures should never be conflated.
Stability and the blue-violet tell
Stability is part of dose context because a degraded complex is not the studied molecule. GHK-Cu has a very high copper stability constant (about log K 16.4), far higher than free GHK, which limits pro-oxidant free-copper release; it is most stable near pH 5-6.5 at a 1:1 copper-to-peptide ratio [11]. The blue-violet color of a reconstituted solution is the expected Cu(II) d-orbital absorption and indicates an intact complex, whereas a brown or green shift indicates oxidation or precipitation [11].
Delivery engineering is the active frontier precisely because native penetration is poor (free GHK clogP -2.24): palmitoylation (Pal-GHK, clogP ~1.14), liposomal encapsulation [10], ionic-liquid microemulsions [14] and microneedle pretreatment all aim to get more intact complex across the stratum corneum [13]. These are research strategies reported at the formulation level, not usage instructions.