TB-500 Dosage Guide: Research Protocols, Loading Phase and Half-Life
TB-500 is a synthetic fragment of thymosin beta-4, and the honest starting point for any question about TB-500 dosage is that no regulator has approved the peptide for human use, so there is no approved dose to quote. What does exist is a body of measured numbers: human pharmacokinetic and safety data for full-length thymosin beta-4, animal dosing ranges, a documented reconstitution procedure for the lyophilized vial, and a set of seller-level or community-level protocols that are frequently presented as if they came from clinical trials. This guide keeps those three categories apart. It covers the doses that were actually given in published research, why protocols split use into a loading dose and a maintenance phase, how half-life connects to injection frequency, how much water a 5 mg vial needs, and which safety signals and regulatory limits apply.
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TB-500 Dosage in the Published Research
Two different molecules are usually confused in dosing discussions. Thymosin beta-4 (Tbeta4) is a 43-amino-acid peptide found in most human cells, and it has been tested in phase 1 human trials. TB-500 is a shorter synthetic fragment representing an active region of that peptide; the FDA lists it as "thymosin beta-4, fragment (LKKTETQ), also known as TB-500". The fragment has not been through human trials. Every human dose figure in the literature therefore describes the full-length peptide, usually given intravenously, and cannot simply be transferred to a subcutaneously injected fragment.
The most cited human dataset comes from a randomized, placebo-controlled phase 1 study in 40 healthy volunteers, published in 2010. Four cohorts of 10 subjects received a single intravenous dose of synthetic Tbeta4 at either 42, 140, 420 or 1260 mg. For an average 70 kg adult those amounts correspond to roughly 0.6, 2, 6 and 18 mg/kg. After a safety review, each subject then received the same dose daily for 14 days. Adverse events were infrequent and mild or moderate in intensity, there were no dose-limiting toxicities and no serious adverse events, and the pharmacokinetic profile was dose proportional, meaning higher doses produced proportionally higher plasma levels. A second first-in-human study in 54 healthy volunteers used a recombinant human Tbeta4 with a completely different scale: single intravenous doses of 0.05, 0.25, 0.5, 2.0, 5.0, 12.5 or 25.0 micrograms per kilogram, followed by multiple-dose cohorts of 0.5, 2.0 and 5.0 micrograms per kilogram given once daily for 10 days. Adverse events were again mild to moderate, no dose-limiting toxicity occurred, and there was no accumulation with continuous administration.
The gap between those two programs is instructive. One measured doses in hundreds of milligrams per subject, the other in micrograms per kilogram, and both were described as tolerated. Without an approved indication, there is no standardized dose, and the numbers only mean something in the context of the specific molecule, route and study design that produced them.
Animal work is more consistent. A 2016 pharmacology study states that the preferred research dosing range for Tbeta4 appears to be 2 to 12 mg/kg, whether given as a single exposure or repeatedly, and that the most commonly used dosage in animal research is around 6 mg/kg because it produced therapeutic effects without signs of adverse reactions. In that same study, pigs received 6 mg/kg intravenously 30 minutes before surgery and again 6 hours later, from a stock solution prepared at 4 mg/mL in sterile water. Rodent traumatic brain injury models have used 6 mg/kg or 30 mg/kg intraperitoneally, in one protocol on day one and then every third day for four further doses.
| Research setting | Molecule and route | Dose used | Schedule |
|---|---|---|---|
| Phase 1, 40 healthy volunteers | Synthetic Tbeta4, intravenous | 42, 140, 420, 1260 mg per subject | Single dose, then the same dose daily for 14 days |
| Phase 1, 54 healthy volunteers | Recombinant human Tbeta4, intravenous | 0.05 to 25.0 micrograms per kg single dose; 0.5, 2.0, 5.0 micrograms per kg repeated | Single dose, then once daily for 10 days |
| Large-animal surgery model | Tbeta4, intravenous, 4 mg/mL stock | 6 mg/kg | Two doses, 6 hours apart |
| Rodent brain injury models | Tbeta4, intraperitoneal | 6 mg/kg or 30 mg/kg | Day 1, then every third day for four more doses |
| General animal research range | Tbeta4, various routes | 2 to 12 mg/kg, about 6 mg/kg most common | Single or repeated |
TB-500 Loading Dose: Where the Two-Phase Protocol Comes From
A loading dose is a larger or more frequent starting schedule designed to bring tissue levels up faster before settling into a lower maintenance schedule. The logic is standard pharmacology, and it does appear in the thymosin beta-4 trials in a simplified form: subjects received a single intravenous dose for pharmacokinetic measurement and then continued on the same amount daily for 10 to 14 days, which is front-loading rather than intermittent dosing. For the TB-500 fragment itself there is no trial of any kind, so no loading dose has ever been tested, compared or validated. The two-phase structure that circulates online is a protocol convention, and it is worth naming its source clearly.
The reference schedule published for the Dragon Pharma TB-500 (thymosin beta-4) 5 mg vial describes a loading phase of 2 to 2.5 mg twice weekly for 4 to 6 weeks, followed by a maintenance phase of 2 to 2.5 mg once weekly. That is 4 to 5 mg per week during loading and 2 to 2.5 mg per week afterwards. With 5 mg vials, the loading phase consumes roughly one vial per week, while maintenance stretches a vial over about two weeks. These figures describe a research-handling convention, not a finding from a controlled study, and the absence of a human dataset for the fragment means the claimed faster onset cannot be verified.
| Phase | Reference schedule | Weekly amount | Basis |
|---|---|---|---|
| Weeks 1 to 4 or 6, loading | 2 to 2.5 mg twice weekly | 4 to 5 mg | Protocol convention; front-loading logic borrowed from the single-dose-then-daily design of the phase 1 trials |
| Week 7 onward, maintenance | 2 to 2.5 mg once weekly | 2 to 2.5 mg | Protocol convention; no comparative data in humans |
| Vial planning | 5 mg lyophilized vial | About 1 vial per loading week, about 1 vial per 2 maintenance weeks | Simple arithmetic on the stated vial size |
| Documented clinical analogue | Synthetic Tbeta4, intravenous, 42 to 1260 mg | Same dose every day for 10 to 14 days | Published phase 1 protocols, full-length peptide only |
TB-500 Injection Frequency: What Actually Drives the Gap Between Doses
Injection frequency in the research record splits by design rather than by principle. Multiple-dose human phases were daily: 10 consecutive days in the recombinant Tbeta4 study and 14 consecutive days in the earlier trial. Animal protocols varied far more, including two doses six hours apart in a surgical model and a five-dose course spaced every third day in a brain injury model. Research-community protocols for the fragment typically settle on twice weekly during a loading phase and once weekly afterwards, which is a slower rhythm than any human study and a faster one than some animal studies.
Three factors explain why these schedules diverge. The first is route: all human pharmacokinetic data come from intravenous administration, which delivers the peptide directly to circulation, whereas a subcutaneous injection is absorbed through tissue and produces a slower, flatter plasma profile. No published study has measured subcutaneous kinetics for the TB-500 fragment, so no protocol interval is derived from measured subcutaneous behaviour. The second is half-life, discussed below, which is short and therefore argues for frequent administration. The third is the assumed duration of the downstream biological effect, which animal models suggest outlasts the presence of the peptide in plasma and is the usual justification for weekly spacing.
Two practical points follow from that. First, because the evidence base is thin, a missed week is not a documented reason to double the next amount; no trial has tested catch-up dosing of this peptide. Second, whatever schedule is followed in a laboratory setting, the material should be measured with a proper syringe, handled aseptically, rotated between sites, and logged with date, amount and concentration so that any reaction can be traced back to a specific vial and volume.
TB-500 Half Life and Why It Shapes the Protocol
The plasma half-life of full-length thymosin beta-4 in humans is measured in hours, and it increases with dose. Reporting on the phase 1 single-dose data, a 2012 review gives mean plasma half-lives of about 0.95 hours at 42 mg per subject, 1.2 hours at 140 mg, 1.9 hours at 420 mg and 2.1 hours at 1260 mg. In other words, the peptide clears quickly and the half-life roughly doubles across the dose range, which is why the trial authors described dose-proportional pharmacokinetics with an increasing half-life. Product listings sometimes quote a figure closer to two days for TB-500; that number reflects an assumption about how long the tissue-level effect persists, not how long the peptide remains in plasma. The two are different things, and only the plasma figure has been measured.
There is a second, more important limitation. The FDA's compounding safety assessment states that it has not identified any human exposure data for drug products containing thymosin beta-4, fragment, and that the agency lacks the information needed to know whether the fragment would harm humans. A half-life is a basic dose-setting parameter, and for the fragment none has been established in humans. Figures circulating online are extrapolations from the full-length peptide, from animal studies, or from neither.
This is why half-life and injection frequency have to be read together. A compound with a one to two hour plasma half-life would normally be dosed daily or more often if plasma exposure were the goal. Weekly or twice-weekly spacing assumes that the relevant activity happens downstream of plasma clearance, in cell migration and tissue repair processes that outlast the peptide itself. That assumption has support in animals and no direct confirmation in humans, which is precisely the uncertainty a dosing table cannot resolve.
Reconstitution: Water Volume, Concentration and Storage Timeline
TB-500 is supplied as a lyophilized powder in a sealed vial and has to be dissolved before any laboratory use. The standard diluent for this purpose is bacteriostatic water with 0.9% benzyl alcohol, which acts as a bacteriostatic preservative and allows the vial to be entered more than once; the manufacturer's labeling for this diluent describes it as a multiple-dose container from which repeated withdrawals may be made. Two warnings from that same labeling matter here: solutions containing benzyl alcohol must not be used in neonates because of preservative toxicity, and bacteriostatic water must not be given intravenously without additives that make the mixture approximately isotonic, since plain water injected intravenously can cause hemolysis.
Concentration is simple arithmetic: the amount of peptide in the vial divided by the volume of water added. Reconstituted at 1 mL a 5 mg vial sits at 5 mg/mL, at 2 mL at 2.5 mg/mL, at 2.5 mL at 2 mg/mL and at 5 mL at 1 mg/mL. The table below shows the same calculation plus the volume that corresponds to a 2.5 mg draw at each concentration.
| Water added to a 5 mg vial | Concentration | Volume for a 2.5 mg draw | Volume for a 1 mg draw |
|---|---|---|---|
| 1 mL | 5 mg/mL | 0.5 mL | 0.2 mL |
| 2 mL | 2.5 mg/mL | 1.0 mL | 0.4 mL |
| 2.5 mL | 2 mg/mL | 1.25 mL | 0.5 mL |
| 5 mL | 1 mg/mL | 2.5 mL | 1.0 mL |
A blended vial behaves differently and this is easy to overlook. The BPC-157 plus TB-500 blend contains 5 mg of each peptide, so 10 mg of total powder. Adding 2 mL of diluent produces 5 mg/mL of combined peptide, and every draw contains both compounds in the same fixed ratio. The blend cannot be used to adjust the TB-500 amount on its own without changing the BPC-157 amount in the same proportion.
Technique follows standard peptide handling. Let the vials reach room temperature, swab both stoppers with alcohol, release the water along the glass instead of onto the cake, then roll the vial gently between the palms until the powder dissolves. Do not shake: vigorous agitation promotes foaming and aggregation, and aggregation is one of the specific safety concerns the FDA raised about this fragment. The dissolved solution should be clear; cloudiness, particles or a colour change mean the vial should be discarded.
For storage, the powder keeps far longer than the solution. Lyophilized peptide should be kept cold and dry in the dark, while a reconstituted vial is more vulnerable to hydrolysis and should be refrigerated, protected from light and not repeatedly frozen and thawed. Dragon Pharma states a multi-use window of up to 28 days for a vial prepared with its bacteriostatic water, which is the practical planning figure for a 5 mg vial used at 2 to 2.5 mg per week. Beyond the storage window, the supply side carries its own risk: unverified sellers can ship diluted, mislabelled or contaminated material, and no protocol can compensate for an unknown powder.
Overdose Signals, Risks and Regulatory Status
There is no defined overdose threshold, no antidote and no toxicology dataset for TB-500, so it is not possible to name a maximum amount. The closest human exposure figures come from the full-length peptide: single intravenous doses up to 1260 mg per subject, and daily dosing at the same level for 14 days, were tolerated with mild to moderate adverse events. Those subjects were healthy volunteers under clinical supervision, given a different molecule by a different route, and the result does not translate into a safe upper limit for a subcutaneously injected fragment.
Known safety concerns are specific rather than theoretical. The FDA placed thymosin beta-4, fragment (LKKTETQ) in Category 2 of its interim compounding lists, meaning compounded products containing it may present significant safety risks, citing the potential for immunogenicity for certain routes of administration due to aggregation, along with peptide-related impurities, and adding that it has not identified human exposure data for the fragment and lacks the information needed to know whether it would harm humans. Animal work at high doses has also shown a vasoconstrictor effect on mesenteric arteries, a vasodilator effect on coronary arteries, and reduced blood clot firmness when an antiplatelet agent was present at the same time.
Because injections bypass the body's first barriers, these are the signals that justify stopping and seeking medical assessment rather than adjusting a dose:
- Allergic or immune reaction - rash, hives, swelling of the face, lips or throat, wheezing or difficulty breathing, fever or new joint pain after an injection
- Injection site infection - pain, redness, warmth or swelling that increases over days, pus, tracking redness, or fever with a painful site
- Bleeding signals - unusual bruising or prolonged bleeding from small cuts, particularly alongside aspirin, anticoagulants or other antiplatelet medication
- Cardiovascular or systemic symptoms - chest pain, shortness of breath, palpitations, sudden severe headache or visual change
- Contaminated material - any vial with a damaged crimp, cloudy solution, or unknown source should be discarded rather than used
The regulatory position is unambiguous. TB-500 is not an approved medicine anywhere; the FDA has not permitted it for human use, and thymosin beta-4 together with its derivatives, TB-500 included, appears on the WADA Prohibited List under class S2, the peptide hormone and growth factor class, so it is banned in sport at all times. This article is a reference summary of published research and product handling information. It is not medical advice, and it is not an instruction to use a research chemical in a human being.