# GHK-Cu Research-Dose Context: Concentrations, Routes and Half-Life > GHK-Cu research-dose context: collagen synthesis onset at 10^-12 M in fibroblasts, topical formulations of 0.05-2%, and rodent systemic doses by route. The concentrations and pharmacokinetics the literature records — research framing only. 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. --- An apothecary's folio of the GHK-Cu copper-tripeptide literature — each collagen assay, hair-count delta and stability constant set out as an engraved plate and weighed against its source, with no dispensary behind the counter and nothing here to dispense.