FOXO4-DRI Reconstitution: How Much Bacteriostatic Water
A 10 mg vial of FOXO4-DRI reconstituted with 2 mL of bacteriostatic water gives a concentration of 5 mg/mL; with 1 mL it gives 10 mg/mL. The calculation depends only on the quantity in the vial and the volume of water added, so the figures below apply to any 10 mg vial.
There is no single correct volume. Adding more water does not change how much is in the vial. It spreads the same quantity through a larger volume, which changes how many syringe units correspond to a given amount. The tables on this page use volumes that produce round numbers on a U-100 syringe; other volumes work identically as long as the resulting concentration is written on the vial.
Peptide reconstitution calculator
Set to this vial below. Change the vial size, water volume, amount or syringe and it recalculates the concentration and the syringe units. For laboratory research use only.
All products are sold strictly for laboratory research use only and are not for human or veterinary consumption. This calculator is provided as a general reference tool.
How much bacteriostatic water for 10 mg FOXO4-DRI?
A 10 mg FOXO4-DRI vial is commonly reconstituted with 2 mL of bacteriostatic water, which gives 5 mg/mL; 1 mL gives 10 mg/mL, 2.5 mL gives 4 mg/mL and 5 mL gives 2 mg/mL. At 5 mg/mL each 0.1 mL of solution contains 0.5 mg.
| Water added | Concentration | Amount in 0.1 mL (10 units on a U-100 syringe) |
|---|---|---|
| 1 mL | 10 mg/mL | 1 mg |
| 2 mL | 5 mg/mL | 0.5 mg |
| 2.5 mL | 4 mg/mL | 0.4 mg |
| 5 mL | 2 mg/mL | 0.2 mg |
For any other volume, the calculator on this page works out the concentration. Before choosing a larger volume, check that the vial has headspace for it. One multi-dose vial of bacteriostatic water covers several research vials.
Reading the concentration on a U-100 syringe
A U-100 insulin syringe is graduated in units, and 100 units equal 1 mL. Units are therefore millilitres multiplied by 100: 0.1 mL is 10 units and 0.25 mL is 25 units. A 0.5 mL syringe carries 50 units and a 0.3 mL syringe carries 30 units on the same scale, with finer markings that make small volumes easier to read.
To find the volume that contains a given amount, divide the amount by the concentration. At 5 mg/mL (a 10 mg vial with 2 mL of water), the volume that contains 1 mg is 1 divided by 5, which is 0.2 mL, or 20 units. The table below runs the same calculation for four arbitrary amounts. They illustrate the arithmetic and nothing else.
| Amount (illustrative) | Volume at 5 mg/mL | U-100 units |
|---|---|---|
| 0.25 mg | 0.05 mL | 5 units |
| 0.5 mg | 0.1 mL | 10 units |
| 1 mg | 0.2 mL | 20 units |
| 2 mg | 0.4 mL | 40 units |
Volumes below about 0.1 mL are hard to read accurately on a 1 mL syringe. Either move to a 0.3 mL or 0.5 mL syringe, or reconstitute with more water so that the same mass occupies a larger, more legible volume.
FOXO4-DRI is described here as a lyophilised material for laboratory research use only. The quantities on this page illustrate the arithmetic of dilution and measurement only.
The FOXO4-DRI vial
FOXO4-DRI is commonly supplied in research catalogues as a 10 mg lyophilised vial. Vistara Labs does not currently stock FOXO4-DRI, but you can request it: contact us and we will source it for you. The calculator on this page works for any vial. The compounds we do carry are listed in the peptide library.
What FOXO4-DRI is
FOXO4-DRI is a synthetic peptide first described in 2017 by Peter de Keizer’s group at Erasmus University Medical Center in Rotterdam. It copies the region of the FOXO4 protein that binds p53, built from D-amino acids in reversed order (a D-retro-inverso peptide) and joined to a cationic cell-permeability sequence. Senescent cells lean on the FOXO4 and p53 interaction to stay alive, and FOXO4-DRI is researched as a senolytic, a compound that clears senescent cells. Its published research is in cell culture and animal models.
- The original study identified FOXO4 as a pivot in senescent cell viability: the peptide caused p53 nuclear exclusion and apoptosis selectively in senescent cells, and in animal models it neutralised doxorubicin-induced chemotoxicity and restored fitness, fur density and renal function in both fast-ageing and naturally aged animals (Baar et al., 2017).
- In chondrocytes from healthy human donors expanded in culture, FOXO4-DRI removed more than half of the cells after extended expansion (population doubling level 9) without significantly changing the number of minimally expanded cells, and significantly lowered the senescence level (Huang et al., 2021).
- In senescent Leydig cells, FOXO4-DRI selectively induced p53 nuclear exclusion and apoptosis, and in naturally aged animals it improved the testicular microenvironment and alleviated age-related testosterone secretion insufficiency (Zhang et al., 2020).
- NMR structural models show FOXO4-DRI binding the disordered p53 transactivation domain to form a transiently folded complex, with both the FOXO4-derived region and the cell-permeability sequence contributing, and p53 phosphorylation increasing the affinity (Bourgeois et al., 2025).
Reconstitution technique
Let the vial reach room temperature, swab both stoppers, and run the measured water slowly down the inside wall of the vial rather than onto the powder. Swirl or tilt gently until the cake dissolves, never shake, and give any remaining powder a few minutes to settle into solution. Label the vial with the date and the concentration, then keep it refrigerated at 2 to 8 °C and protected from light. The full method, with the reason behind each step, is in how to reconstitute peptides with bacteriostatic water.
Why the solution should look clear
Properly reconstituted FOXO4-DRI forms a clear, colourless solution. Cloudiness, strands or a gel that will not disperse usually mean the water went in too fast or the vial was shaken; haze that appears later points to warm or bright storage. The causes are covered in why peptides gel or go cloudy.
Bacteriostatic water, not sterile water
Bacteriostatic water is sterile water with 0.9% benzyl alcohol, a preservative that allows a refrigerated vial to be accessed more than once; plain sterile water is intended for single access. The difference is explained in bacteriostatic water explained.
Frequently asked questions
How much bac water for a 10 mg FOXO4-DRI vial?
A 10 mg FOXO4-DRI vial is commonly reconstituted with 2 mL of bacteriostatic water, which gives 5 mg/mL; 5 mL gives 2 mg/mL. At 5 mg/mL each 0.1 mL (10 units on a U-100 syringe) contains 0.5 mg.
How many units on a U-100 syringe contain 1 mg at 5 mg/mL?
At 5 mg/mL (a 10 mg vial with 2 mL of water), the volume that contains 1 mg is 1 divided by 5, which is 0.2 mL, or 20 units. Units are millilitres multiplied by 100, so 0.1 mL is 10 units. The amounts on this page illustrate the arithmetic only.
What should reconstituted FOXO4-DRI look like?
Properly reconstituted FOXO4-DRI forms a clear, colourless solution. Cloudiness, strands or a gel that will not disperse usually mean the water went in too fast or the vial was shaken; haze that appears later points to warm or bright storage. More on the causes in why peptides gel or go cloudy.
Can I use sterile water instead of bacteriostatic water?
Only for a vial that will be accessed once. Bacteriostatic water is sterile water with 0.9% benzyl alcohol, a preservative that allows a refrigerated vial to be accessed more than once; plain sterile water is intended for single access. Details in bacteriostatic water explained.
How should a reconstituted FOXO4-DRI vial be stored?
Refrigerated at 2 to 8 °C, protected from light and labelled with the date and the concentration. Unopened lyophilised vials are kept cold and dark until they are needed. The full storage guide is how to store research peptides.
Work it out for a different vial or concentration
Our peptide calculator opens pre-set for a 10 mg vial with 2 mL of water and marks the 1 mg draw of 20 units on a syringe diagram. Change the vial size, water volume, amount or syringe and it recalculates.
For any vial: bacteriostatic water.
Sources: Baar MP et al. Targeted Apoptosis of Senescent Cells Restores Tissue Homeostasis in Response to Chemotoxicity and Aging. Cell. 2017. PMID 28340339. Huang Y et al. Senolytic Peptide FOXO4-DRI Selectively Removes Senescent Cells From in vitro Expanded Human Chondrocytes. Front Bioeng Biotechnol. 2021. PMID 33996787. Zhang C et al. FOXO4-DRI alleviates age-related testosterone secretion insufficiency by targeting senescent Leydig cells in aged mice. Aging (Albany NY). 2020. PMID 31959736. Bourgeois B et al. The disordered p53 transactivation domain is the target of FOXO4 and the senolytic compound FOXO4-DRI. Nat Commun. 2025. PMID 40593617.
All products supplied by Vistara Labs are intended for laboratory research use only. They are not drugs, are not approved for human or veterinary use, and are not intended to diagnose, treat, cure or prevent any condition. Nothing on this page constitutes medical advice or guidance for use in humans.
