> CAT DOSAGE :: RESEARCH-CONTEXT ONLY // NO HUMAN PROTOCOL
TB-500 dosage, half-life, and routes — read straight from the studies, not a protocol.
What was administered, to which species, at which dose, by which route. No human dosing recommendation — the fragment has no validated human protocol.
TB-500 Dosage in the Research Literature
TB-500 dosage figures in the published literature describe what was administered to animals — and, in one case, to humans receiving the full-length protein. They are not human protocols for the fragment, and nothing on this page is a dosing recommendation.
Animal studies dosed full-length thymosin beta-4 across a wide range. The rat embolic-stroke dose-response study used 2, 12, and 18 mg/kg intraperitoneally, starting 24 hours after stroke and repeating every three days for four more doses; 2 and 12 mg/kg improved outcomes, 18 mg/kg did not, and a modeled optimum of ~3.75 mg/kg was proposed [4]. Cardiac and neurological rodent models cluster in the single-digit-mg/kg range. An mdx muscular-dystrophy study used 150 µg twice weekly intraperitoneally for six months. At the other end of the scale, picogram-to-nanogram amounts are bioactive in vitro — roughly 10 pg was active in keratinocyte migration assays [3].
The human number comes from a single Phase 1 study: synthetic thymosin beta-4 given intravenously at 42, 140, 420, and 1260 mg — a single dose, then daily for 14 days — well tolerated throughout [6]. That is the full-length protein, intravenous, in a controlled setting. It is not a TB-500-fragment protocol, and it was not designed to find an effective dose.
The non-monotonic stroke result is the figure worth sitting with: more was not better [4]. The community "loading then maintenance" protocols that circulate in athletic and peptide-research forums are not derived from controlled human trials and have no published clinical validation — the record does not support presenting them as dosing.
TB-500 Half-Life and Pharmacokinetics
TB-500 Half-Life and Pharmacokinetics
No validated human pharmacokinetic half-life exists for the TB-500 heptapeptide. In the intravenous full-length thymosin beta-4 Phase 1 study, pharmacokinetics were dose-proportional and half-life increased with dose [6]. Anti-doping LC-MS work characterizes TB-500 and its metabolites in equine plasma and urine for detection purposes — not for human pharmacokinetics. The fragment's human half-life is, on the record, a NULL value.
The distinction matters because half-life is exactly the kind of number that gets quoted with false precision. For the TB-500 fragment specifically, there is no validated human figure to quote. What exists is dose-proportional pharmacokinetics for the full-length protein given intravenously [6], and analytical detection windows for the fragment in horses. Neither yields a human half-life for the 7-mer.
The short acetylated structure of the fragment makes it more chemically robust than the full-length protein, which can shorten in vivo persistence assumptions people carry over from the protein — but chemical robustness is not a measured pharmacokinetic parameter, and inferring a human half-life from it would be a fabrication. The honest readout for the fragment's validated human half-life is the one the terminal renders for it: NULL. Where a precise figure would normally sit, the record is empty.
Routes studied and material handling
The routes that appear in the research record are specific to the studies, not endorsements. Intraperitoneal injection predominates in the rodent efficacy work [3][4]. Intravenous administration appears in the human Phase 1 study and some cardiac models [6]. Topical and ophthalmic routes appear in corneal and dermal wound work and the dry-eye trials of full-length thymosin beta-4 (RGN-259) [8]. Subcutaneous and intramuscular routes circulate as community research-use routes but do not come from controlled human efficacy trials.
Research-grade TB-500 is supplied as 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 remains subject to proteolysis and freeze-thaw degradation. Identity and purity of research-grade material are a recurring concern — peptide identity, correct sequence, and full-length-versus-fragment confusion are not guaranteed in unregulated supply, which also complicates interpreting any anecdotal result. This page describes what studies administered; it does not tell anyone what to administer.