Accepted answer
10 ÷ 1 = 10 mg/mL. Concentration is vial content divided by diluent volume, so 10 mg of peptide in 1 mL of 0.9% sodium chloride gives 10 mg/mL. On a U-100 barrel one unit is 0.01 mL, so one unit of this solution carries 0.1 mg — 100 µg. That is the number to write on the label, because you will not reconstruct it from memory at an awkward moment.
Before anything else: a kitchen counter with an alcohol wipe is not an aseptic environment, and it is worth being honest about that rather than pretending the procedure is something it is not. What you are doing is reducing bioburden, not achieving sterility.
Room temperature before drawing is worth the ten minutes. Cold solution is more viscous, draws slower, and is more likely to pull a bubble past the plunger seal.
Concentration and unit conversion at a glance
| Vial | Diluent | Concentration | 0.25 mg | 0.5 mg | 1 mg | 2.5 mg |
|---|
| 5 mg | 1 mL | 5 mg/mL | 5 u | 10 u | 20 u | 50 u |
| 5 mg | 2 mL | 2.5 mg/mL | 10 u | 20 u | 40 u | 100 u |
| 10 mg | 1 mL | 10 mg/mL | 2.5 u | 5 u | 10 u | 25 u |
| 10 mg | 2 mL | 5 mg/mL | 5 u | 10 u | 20 u | 50 u |
| 10 mg | 3 mL | 3.33 mg/mL | 7.5 u | 15 u | 30 u | 75 u |
Units are U-100 insulin units, where 1 unit = 0.01 mL. Divide dose by concentration for millilitres, then multiply by 100.
Do not use the same needle to pierce the stopper and to administer.
The 28-day beyond-use convention for a multiple-withdrawal preserved preparation derives from USP compounding chapters, which set it on microbiological risk rather than chemical stability.
None of this is exotic. It is just the difference between doing it deliberately and doing it approximately.
Adding that a fixed-needle syringe loses about a tenth of what a luer one does. – coldpack_88 3 months ago 8The dead-space number surprised me until I did the multiplication across twenty draws. – meniscus_film 41 days ago add a comment