Peptides
Thymosin Alpha-1
Also called Tα1 · Thymalfasin · Zadaxin
Thymosin Alpha-1 is sought for immune support, particularly by people worried about repeated infections or poor recovery after illness. It has disease-specific medical use and research, but “supports immunity” is not proof that it prevents routine infections or fixes unexplained fatigue.
Dosage & duration
Indonesian Zadaxin product-label example for chronic hepatitis B.
Adults with chronic hepatitis B
Product label- Dose
- 1.6 mg
- How often
- Twice weekly, under the skin; doses 3–4 days apart
- How long
- Six months
Compensated liver disease and evidence of HBV replication; not a routine immune-wellness cycle.
Sources: 1
An illness-specific regimen does not establish a dose for general infection prevention.
Immune support
Fewer infections and a better recovery?
-
Repeated infections
People hope to get ill less often, but routine infection prevention is not established by disease-specific treatment studies.
-
Recovery after illness
Persistent fatigue is another reason for interest; that does not establish that thymosin alpha-1 will resolve it.
Why people are interested
The appeal is helping an underperforming immune response rather than directly killing a virus or bacterium. The important question is which condition is being treated and whether outcomes improved—not simply whether an immune marker changed.
What the named medicine is used for
The Indonesian Zadaxin label covers adults with chronic hepatitis B and compensated liver disease. That is specific medical treatment. It does not establish the same six-month plan for healthy people, fatigue, a cold or post-viral symptoms.
Why immune boosting is too simple a promise
Immune responses can be inadequate, excessive or misdirected. The label cautions about deliberately immunosuppressed patients, including transplant recipients. Severe-infection research also uses very different patients and regimens from outpatient wellness use.
Model details: Thymosin Alpha-1 · relative timing
Compare timing and buildup for this compound. The values are not blood concentrations or a measure of strength.
Shows a relative timing scenario; absolute blood concentrations are not calibrated.
Timing assumptions and sources
Rost 1999: nine Caucasian volunteers,900 microgram/m² SC, three-way formulation crossover, single and 5 day administration; Tmax 1–2 h, half-life<3 h. Use 2 h/1.5 h as explicitly inferred representative timing, not a reported fitted parameter pair.
One 1 mg input peaks at 1 relative unit after a single dose. Other amounts scale proportionally; overlapping doses add when accumulation is on. Different compounds use separate relative scales.
- Timing half-life used
- 2 hours
- Absorption half-life assumed
- 0.6075545 hours
- Reference amount for the relative scale
- 1 mg
- The faster rate is inferred to match the 1.5 h source-scoped peak time; absorption half-life 0.6075545274580504 h is a mathematical shape parameter, not separately measured.
- A single 1-unit input has a peak of 1 relative unit; scaling and repeated-dose addition are mathematical assumptions. This normalization is independent of the example dose.
- Zadaxin/Timosina/Talpha 1-HLR show different exposure.
- The 63 ng/mL at 1.6 mg value is present in a 2024 review but primary product/cohort linkage was not established in this pass.
- Apparent volumes/clearance already include F.
- Pharmacokinetics of thymosin alpha1 after subcutaneous injection of three different formulations in healthy volunteers.
Rost 1999: nine Caucasian volunteers,900 microgram/m² SC, three-way formulation crossover, single and 5 day administration; Tmax 1–2 h, half-life<3 h. Use 2 h/1.5 h as explicitly inferred representative timing, not a reported fitted parameter pair.
- FDA2024 thymosin-alpha1 scientific review
Clinical and formulation evidence reviewed; original Rost citation located. Rat PK and salt/free-base distinctions must not calibrate this human entry.
thymosin-alpha-1-relative-timing-2026-10 · version 1
Common questions
Is Thymosin Alpha-1 the same as TB-500?
No. Thymosin Alpha-1 and thymosin beta-4-related products are different compounds.
Does the hepatitis dose prove a general immune-support cycle?
No. A dose studied or labelled for one disease does not establish effectiveness for routine wellness use.
Sources Labels, studies and notes behind this guide
Catalog evidence: Human clinical trials. This describes the type of evidence, not a clinical review of every claim.
Summary and fact source checks: 2026-10-07. This records source checking, not medical review of the whole page.
Notes on the quick facts
- Common interest
- The condition and meaningful outcome must be specified.
- Named product
- Country-specific disease indications matter.
- Not the same peptide
- Alpha-1 and beta-4 are not interchangeable.
- 1. Zadaxin label hosted by Indonesian regulator
Chronic hepatitis B in adults with compensated liver disease; 1.6 mg SC twice weekly six months. Not a general-wellness indication.
- 2. TESTS randomized sepsis trial
Hospital sepsis setting; primary report and correction locator reviewed. No general infection-prevention claim drawn from trial.
- 3. TESTS correction notice
Correction acknowledges data verification/database errors; original numerical outcomes not copied into guide.
- 4. Pharmacokinetics of thymosin alpha1 after subcutaneous injection of three different formulations in healthy volunteers.
Rost 1999: nine Caucasian volunteers,900 microgram/m² SC, three-way formulation crossover, single and 5 day administration; Tmax 1–2 h, half-life<3 h. Use 2 h/1.5 h as explicitly inferred representative timing, not a reported fitted parameter pair.
- 5. FDA2024 thymosin-alpha1 scientific review
Clinical and formulation evidence reviewed; original Rost citation located. Rat PK and salt/free-base distinctions must not calibrate this human entry.
- 6. Rost et al.: thymosin alpha1 formulation PK
Nine healthy volunteers, randomized three-formulation SC crossover; peaks 1–2 hours and half-life <3 hours, with formulation differences.
- 7. TESTS phase 3 thymosin alpha1 sepsis trial, 2025
1106 randomized adults; no clear reduction in 28-day all-cause mortality. Indication-specific negative primary result.
Related compounds and examples
Related compounds
LL-37 (Cathelicidin)
LL-37 for immune, gut and wound-healing questions: what people seek, reported injection amounts and what topical human trials actually found.
KPV
KPV for gut and skin concerns: oral versus injected products, reported dose context and realistic expectations for inflammation claims.
Thymalin
Thymalin for immune support and healthy-aging questions: the reported short course, product differences and what the clinical study can tell you.