# TB-500 Dosage in the Research Literature, Half-Life, and Routes | TB-500 > TB-500 dosage as studied in animals and one human Phase 1: the mg/kg ranges, the non-monotonic stroke data, the routes, and why no validated human half-life exists for the fragment. 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. --- A phosphor-terminal reading of the TB-500 record — the Ac-LKKTETQ fragment logged green where its studies hold, every full-length thymosin beta-4 substitution flagged as a checksum mismatch, and the empty human-trial line left blinking NULL; no clinic behind the screen and nothing here dispensed or sold.