What Thymosin Alpha-1 is
Thymosin alpha-1 is a 28-amino-acid fragment of prothymosin alpha with a genuine clinical record: approved as Zadaxin in more than 35 countries for hepatitis B and C and as an immune adjuvant, with decades of human use at 1.6 mg twice weekly. It is not FDA approved, and in 2023 it was placed in 503A category 2, ending US compounding pharmacy access and pushing users to the gray market.
What we do not know
- Approved in roughly thirty countries but not the United States, so the evidence has never been through FDA review.
- Trial quality varies sharply by indication. The hepatitis data is the strongest; sepsis and oncology adjuvant results are mixed.
- COVID-era work is largely observational and small.
Reconstitution math
Concentration is everything: the same 5 mg vial gives a different draw for every amount of bacteriostatic water you add. The table uses the common 2 mL setup for each vial size, which puts every unit on a U-100 insulin syringe at 25 mcg for the default vial. Dashes mark draws too small to measure or larger than the syringe.
| Vial | BAC water | Concentration | 0.8 mg | 1.6 mg | 3.2 mg |
|---|---|---|---|---|---|
| 5 mg | 2 mL | 2.5 mg/mL | 32 u | 64 u | - |
| 10 mg | 2 mL | 5 mg/mL | 16 u | 32 u | 64 u |
Dosing and protocol
Zadaxin label dose is 1.6 mg subcutaneously twice weekly; community immune protocols mirror it.
The clinical dose is 1.6 mg subcutaneously twice weekly, which on a 5 mg vial with 2 mL of water is a 64-unit draw. Community immune support protocols use the same dose and cadence, sometimes at half dose. Its two-hour half-life means each dose is a discrete immune signal, not a maintained level; accumulation math does not apply.
Pharmacokinetics
Thymosin Alpha-1 has published human pharmacokinetics: peak about one to two hours after a subcutaneous dose; half-life around two hours. The curves below are normalized one-compartment models built from the cited half-life, the same math the Planner uses. They show shape and timing, not absolute blood levels.
How it is thought to work
Thymosin alpha-1 is a thymic peptide that modulates T-cell maturation and dendritic cell function. It is approved in a number of countries for hepatitis B and C and as an immune adjuvant, though not by the FDA.
What the evidence supports
This table grades how well each outcome has been studied in humans, not how well Thymosin Alpha-1 works. A strong grade means the question was asked properly, and the answer may still have been negative. Nothing here is inherited from a drug class, a close analog, or the parent molecule of a fragment.
| Outcome | Strongest published evidence |
|---|---|
| Chronic hepatitis B | Human RCT |
| Immune modulation markers | Human RCT |
| Sepsis outcomes | Human RCT |
| COVID-19 outcomes | Human, observational |
Storage and handling
Lyophilized vials keep best cold, dark, and dry; refrigeration is the community default and freezing lyophilized powder is common for long holds. After reconstitution, refrigerate at 2 to 8 C, do not freeze the solution, and date the vial. Bacteriostatic water's preservative keeps multi-dose use practical for about 28 days by USP convention, though our 120-day stability study found the preservative itself outlasts that window.
Got a certificate of analysis with your vial? Run it through our COA Reader: it reads the report in plain English, checks purity and mass against the label claim, and links the testing lab’s own verification page. Our guide to reading a COA explains what the numbers do and do not tell you.
Sources
- Zadaxin prescribing information (SciClone Pharmaceuticals)Prescribing information
- King and Tuthill, Immune modulation with thymosin alpha 1 treatment, Vitam Horm 2016PMID 27450734 · DOI
- FDA 503A bulk substances category 2 listing (2023)