how much of what we believe about bacteriostatic water actually comes from dead space threads
how much of what we believe about bacteriostatic water actually comes from dead space threads. If this has been answered properly somewhere, link me and I will delete.
If your calculation produces a fraction of a unit, the concentration is wrong for your dose. Change the water volume until the numbers land on whole 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 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.
That is everything I have. The rest is opinion and I have tried to keep it out.
best — the order this archive was captured in
Research-use-only material is not approved for human use, so treat everything in this thread as arithmetic about solutions rather than instructions for a person.
The arithmetic in full: concentration is mass over volume, so 20mg into 2mL gives 10mg/mL. A U-100 syringe is graduated at 100 units per millilitre, so 1mg is 1 divided by 10 millilitres, which is 10 units.
Working has to be shown on arithmetic posts. Added a note asking for it rather than removing this one.
do the arithmetic before you reconstitute, not while holding a syringe
reconstituting at a round concentration makes every later dose easy
more water is not more drug, it is the same drug in a bigger volume
How many mg in the vial and how many mL are you adding?
Small fix — a U-100 syringe is 100 units per mL. If yours is marked differently it is not U-100 and the whole calculation changes.
a U-100 syringe reads 100 units to the millilitre, every time
Aim the stream down the wall of the vial rather than into the cake. Reconstitution is a solubility problem, not a mixing problem, and mechanical shear does nothing helpful.
dead space in the needle hub is real and it is small
Same. I got this wrong once, caught it because the units looked absurd, and have written on every vial since.
Cosigning the round-number approach. Reconstituting to something awkward is how you end up drawing 27.5 units at six in the morning.
Cosigning the round-number approach.
Adding one thing — put the date on the label too. Concentration plus date and you can never mix two vials up.
Yes. Writing 10mg/mL on the vial takes four seconds and removes the entire class of error this board exists to fix.
Yes, and the dead-space point is worth repeating: it is small, it is real, and it is the same for every draw.
Right — the volume you add is the only variable you control here, and the cake does not change it meaningfully.
This. Showing the working is the fastest way for somebody else to spot the mistake.
Did the maths give you a whole number of units, or a fraction?
- 1Working has to be shown on arithmetic posts. Added a note asking for it…10 comments in this branch · started by u/swirl_dont_shake