Thymosin alpha-1 reconstitution: the Zadaxin label's 1.6 mg in 1 mL, then 5 mg and 10 mg vials at 1–3 mL, the 1.6 mg dose in units and amounts per vial.
Thymosin alpha-1 is unusual among the compounds on this site: an approved product exists, sold outside the United States as Zadaxin, and its label states exactly how the powder is mixed. That gives the arithmetic a fixed reference point — 1.6 mg in 1 mL, used at once — against which the 5 mg and 10 mg research vials can be measured. This page reports the label's figures (prescribing information as reproduced on RxList, read 2026-10-12), works the research vials at the calculator's water volumes, converts the label dose into syringe units at each concentration, and counts how many label-sized amounts each vial holds. It reports; it suggests no dose.
The dose record itself — the hepatitis programme, the 1,106-patient sepsis trial and the regulatory history — is on the thymosin alpha-1 dosage page. The arithmetic for any other vial or volume is on the thymosin alpha-1 calculator; the index of every compound is the reconstitution hub.
What the label states
| Item |
Zadaxin label |
| Vial content |
1.6 mg thymosin alpha-1, 50 mg mannitol, sodium phosphate buffer to pH 6.8 |
| Diluent |
1.0 mL sterile water for injection, supplied in an ampoule |
| Final concentration |
1.6 mg/mL |
| Use |
Single-use vial; "should be used immediately" after reconstitution |
| Route |
Subcutaneous; "should not be given intravenously" |
| Dose |
1.6 mg (900 mcg/m²) twice a week, 6–12 months; 40 mcg/kg under 40 kg |
| Storage before mixing |
2–8 °C |
Two consequences follow. The labelled dose is the entire contents of one vial, so the label never needs a syringe-unit reading — the whole 1 mL is drawn. And the label's diluent is sterile water without a preservative, which matches a vial that is emptied in one draw. A 5 or 10 mg research vial is the opposite case: several amounts drawn over days, which is the situation bacteriostatic water exists for and which no thymosin alpha-1 label describes.
Water per vial and the concentration it gives
| Vial |
Water |
Concentration |
mcg per U-100 unit |
| 1.6 mg (Zadaxin) |
1 mL |
1.6 mg/mL |
16 |
| 5 mg |
1 mL |
5 mg/mL |
50 |
| 5 mg |
2 mL |
2.5 mg/mL |
25 |
| 5 mg |
3 mL |
1.67 mg/mL |
16.7 |
| 10 mg |
1 mL |
10 mg/mL |
100 |
| 10 mg |
2 mL |
5 mg/mL |
50 |
| 10 mg |
3 mL |
3.33 mg/mL |
33.3 |
On a U-100 syringe, 100 units is 1 mL (MedlinePlus, "Giving an insulin injection", reviewed 2024-07-21). To reproduce the label's 1.6 mg/mL a 5 mg vial would need 3.125 mL of water and a 10 mg vial 6.25 mL — more than most research vials hold. At 5 mg with 3 mL, the closest standard volume, the concentration is 1.67 mg/mL, about 4% stronger than the label's.
The trial and label amounts in syringe units
Three amounts appear in the record: 1.6 mg (the label and the sepsis trial), and 0.8 and 3.2 mg (the low and high arms of a 12-week hepatitis C dose-ranging study reported by the manufacturer). Converted at each concentration:
| Concentration |
0.8 mg |
1.6 mg |
3.2 mg |
| 1.6 mg/mL (label) |
50 units |
100 units |
200 units, two barrels |
| 1.67 mg/mL (5 mg in 3 mL) |
48 units |
96 units |
192 units |
| 2.5 mg/mL (5 mg in 2 mL) |
32 units |
64 units |
128 units |
| 3.33 mg/mL (10 mg in 3 mL) |
24 units |
48 units |
96 units |
| 5 mg/mL (5 mg in 1 mL, 10 mg in 2 mL) |
16 units |
32 units |
64 units |
| 10 mg/mL (10 mg in 1 mL) |
8 units |
16 units |
32 units |
The label's weight-based dose for patients under 40 kg is 40 mcg/kg: 1.2 mg at 30 kg, which is 75 units at 1.6 mg/mL or 48 units at 2.5 mg/mL.
Amounts per vial
Whatever the water volume, the powder sets how many label-sized amounts a vial holds:
| Vial |
1.6 mg amounts |
Left over |
On a twice-weekly schedule |
| 1.6 mg (Zadaxin) |
1 |
0 |
One vial per dose; two vials a week |
| 5 mg |
3 |
0.2 mg |
About 1.5 weeks |
| 10 mg |
6 |
0.4 mg |
About 3 weeks |
The sepsis trial's schedule, 1.6 mg every 12 hours for seven days, is 14 amounts and 22.4 mg in a week — fourteen label vials, or four and a half 5 mg vials. Adding more water to a research vial makes each draw larger in units, not more numerous.
Mixing, as the label describes it
The Zadaxin label directs the supplied 1 mL diluent into the vial immediately before use. The general procedure for a lyophilized peptide — diluent down the side of the vial, swirled rather than shaken, inspected for clarity — is on Medibact's how to reconstitute peptides page and is not repeated here. One point specific to this label: the vial also contains 50 mg of mannitol, so dissolved solids add slightly to the final volume; the label states the result as 1.6 mg/mL all the same, and the calculator, like every calculator, treats the water volume as the final volume.
Storage after mixing
The only label statement is the label's own: use the reconstituted single-use vial immediately. No label addresses a multi-dose thymosin alpha-1 vial; what labels and manufacturers say about storing reconstituted peptides is on Medibact's how to store peptides page.
What this page does not do
It does not state or suggest an amount, a frequency or a course. The 1.6 mg figure is reported because a label states it for hepatitis B and C in the countries where Zadaxin is approved; thymosin alpha-1 has no US approval, and FDA lists it among bulk substances that may present significant safety risks for compounding. The arithmetic is exact for the inputs given and says nothing about whether any input is appropriate. Medibact's thymosin alpha-1 guide covers the compound. Product and dose decisions belong with a clinician.
Sources and dates
Opened 2026-10-12: the Zadaxin (thymalfasin) prescribing information as reproduced on RxList (description, dosage and administration, how supplied, storage, pharmacokinetics); Ancell, Phipps and Young, "Thymosin alpha-1", Am J Health Syst Pharm 2001 (PMID 11381492, abstract); FDA, "Certain bulk drug substances for use in compounding that may present significant safety risks" (content current as of 2026-04-22); MedlinePlus, "Giving an insulin injection" (reviewed 2024-07-21). From this site's dosage page (opened 2026-09-18): the TESTS sepsis trial (PMID 39814420) and the 0.8/1.6/3.2 mg dose-ranging arms in the manufacturer's 2004 annual report. Concentration, unit and per-vial arithmetic by this site. Corrections go to the contact page.
