how much of what we believe about mg/mL actually comes from reconstitution threads
Question in the title, detail here: how much of what we believe about mg/mL actually comes from reconstitution threads.
The arithmetic in full: concentration is mass over volume, so 10mg into 1mL gives 10mg/mL. A U-100 syringe is graduated at 100 units per millilitre, so 2.5mg is 2.5 divided by 10 millilitres, which is 25 units.
Bacteriostatic water contains benzyl alcohol as a preservative, which is what makes repeated entry into the same vial reasonable. Plain sterile water has no preservative.
The whole calculation, once, with real numbers.
You have a 20mg vial. You add 1mL of bacteriostatic water. Concentration is mass over volume: 20mg/mL. A U-100 insulin syringe is graduated at 100 units per millilitre, so one unit is 0.01mL.
To draw 5mg you need 5 divided by 20 millilitres, which is 25 units on the barrel. Write "20mg/mL" on the vial in marker before you put it away, and you never have to do this again for that vial.
Screenshot none of this. Read the whole thread, including the parts where I am told I am wrong.
best — the order this archive was captured in
Why "more water" keeps confusing people, including me for a month.
The vial contains a fixed amount of peptide. Water changes nothing about that amount. What it changes is concentration, and concentration is the divisor between the dose you want and the volume you draw.
So doubling the water halves the concentration and doubles the units for the same dose. Nothing is diluted in any sense that matters; you are simply reading a bigger number off the same barrel. Pick the water volume that puts your usual dose on a whole number of units and life gets easier.
the number you write down is the number you will trust at 6am
Correction: that gives 40 units, not what you have written. 5mg into 2mL is 2.5mg/mL and the division follows from there.
Spent 9 weeks confused about this until somebody drew the table for me. 20mg, 2mL, 10mg/mL, 1mg is 10 units. That is the whole thing.
bacteriostatic water has the preservative, sterile water does not
aim the stream at the glass wall, not at the cake
Yes, and the dead-space point is worth repeating: it is small, it is real, and it is the same for every draw.
Yes, and the dead-space point is worth repeating: it is small, it is real, and it is the same for every draw.
Right, and the arithmetic behind it: 20mg in 2mL is 10mg/mL, so 1.5mg is 15 units.
The lyophilised cake displaces a small volume, so the true concentration is very slightly lower than the arithmetic suggests. It is a fraction of a percent and it is dwarfed by fill tolerance.
5mg into 2mL is 2.5mg/mL, and 0.25mg of that is 10 units