Research context · 04
TB-500 Dosage, Strictly as Reported in the Research
Every figure here is a dose administered to a species in a study. None is a human recommendation, and the community 'loading' protocols have no controlled-trial basis.
TB-500 Dosage in the Research Literature
TB-500 dosage in the research literature is reported almost entirely for the parent protein, thymosin beta-4, and it spans a wide range by species and route. In rodent efficacy models, doses run roughly 6–12 mg/kg in cardiac and neurological studies, with the embolic-stroke dose-response study testing 2, 12, and 18 mg/kg intraperitoneally and modeling an optimum near 3.75 mg/kg [4]. A six-month mdx muscular-dystrophy study used 150 µg twice weekly intraperitoneally. These are doses given to rats and mice, framed here as study parameters and nothing else.
Human dosing exists only from one Phase 1 study, and only for the protein. Synthetic thymosin beta-4 was dosed intravenously at 42, 140, 420, and 1260 mg — a single dose, then daily for 14 days — and was well tolerated across all four cohorts [6]. At the other end of the scale, picogram-to-nanogram amounts are bioactive in vitro: roughly 10 pg was active in keratinocyte migration assays, and nanomolar thymosin beta-4 stimulates hair-follicle stem cells [3].
The range itself — picograms in a dish to 1260 mg intravenously in a person — is the point. There is no single 'dose' for TB-500, and the figures belong to different molecules, routes, and species. This is the TB-500 dosage in the research literature, not a protocol.
Routes studied, and half-life
The routes that appear in the literature are intraperitoneal (the predominant route in rodent efficacy studies), intravenous (the human Phase 1 of full-length thymosin beta-4, and some cardiac models), and topical or ophthalmic (corneal and dermal wound work, and the dry-eye RGN-259 trials, all with the protein) [6]. Subcutaneous and intramuscular routes appear in community research use but not in controlled human efficacy trials.
Half-life is a genuine gap. There is no validated human pharmacokinetic half-life for the TB-500 heptapeptide. In the IV full-length thymosin beta-4 Phase 1 study, half-life increased with dose — the pharmacokinetics were dose-proportional [6] — but that figure describes the protein, not the fragment. Anti-doping LC-MS work has characterized TB-500 and its metabolites, primarily in equine plasma and urine, for detection rather than for human pharmacokinetics.
As supplied, research-grade TB-500 is a lyophilized powder reconstituted in bacteriostatic or sterile water and kept refrigerated. As a short acetylated peptide it is more chemically robust than the full-length protein, but it is still subject to proteolysis and freeze-thaw degradation, and the identity and purity of unregulated material is a recurring concern.
Why 'loading then maintenance' has no evidence behind it
Non-clinical 'loading then maintenance' protocols circulate in athletic and peptide-research communities. They are not derived from controlled human trials and have no published clinical validation. Two findings in the actual literature actively cut against them.
First, the dose response is non-monotonic. In the rat embolic-stroke study, 2 and 12 mg/kg improved neurological outcomes while 18 mg/kg gave no significant benefit, and the modeled optimum sat near 3.75 mg/kg [4]. More is not reliably better, which is precisely the assumption a 'loading' phase makes. Second, more administration did not buy more functional benefit in the mdx model: chronic thymosin beta-4 increased regenerating fibers but did not improve strength, cardiac function, or fibrosis.
The honest position on TB-500 dosage is therefore narrow. Animal doses are documented and species-specific; one human IV protocol exists for the parent protein; no validated fragment half-life exists; and the popular dosing templates have no controlled-trial support and at least two preclinical findings against their core logic. We describe what was administered to which species; we do not translate any of it into a human dose.