the bacteriostatic water question that gets asked weekly, answered properly
the bacteriostatic water question that gets asked weekly, answered properly. Change my mind, genuinely — I have no stake in being right about this. The failure modes I have actually seen posted here, in order of frequency. One: reconstituting at a different volume than intended and not writing it down, so the next…
This. Showing the working is the fastest way for somebody else to spot the mistake.
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.
Started reconstituting everything to a round concentration and the six-in-the-morning error rate went to zero.
the number you write down is the number you will trust at 6am
label the vial with the date as well as the concentration
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 sterile water, not bacteriostatic. Same appearance, different product, and it matters for a multi-draw vial.