genuine question about bacteriostatic water that I am slightly embarrassed to ask
genuine question about bacteriostatic water that I am slightly embarrassed to ask. Searched first, found three threads that contradict each other, hence the post.
Wrote the date on the vial as well as the concentration after losing track of which one was opened first.
Shook the first vial because nobody told me not to. It was fine, but I have swirled every one since.
The dead space question sent me down a rabbit hole for a week. It is a fraction of a unit and it is the same every draw.
Research-use-only material is not approved for human use and nothing here should be read as a recommendation to use it.
best — the order this archive was captured in
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.
I keep a laminated card in the drawer with the arithmetic on it. Looks ridiculous. Has never once let me draw the wrong volume.
units are a volume on a U-100 syringe, not a dose
Working has to be shown on arithmetic posts. Added a note asking for it rather than removing this one.
a U-100 syringe reads 100 units to the millilitre, every time
if the maths gives you a fraction of a unit, change 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.
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.
Are you accounting for the powder volume, or is that where the confusion is?
Reconstituted at 2mL when I meant to use a different volume. Caught it because the units looked wrong on the barrel. Now I write 10mg/mL on the glass before I put the cap back.
bacteriostatic water has the preservative, sterile water does not
Spent 23 weeks confused about this until somebody drew the table for me. 30mg, 3mL, 10mg/mL, 2mg is 20 units. That is the whole thing.
5mg into 1mL is 5mg/mL, and 0.75mg of that is 15 units
more water is not more drug, it is the same drug in a bigger volume
Is that a U-100 syringe? The barrel markings change the answer completely.
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.
more water is not more drug, it is the same drug in a bigger volume
Disagreeing with this line only: adding more water is not a safety margin, it is a different divisor.
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 draw is based on a remembered concentration. Two: treating units as a dose rather than a volume, which breaks the moment the concentration changes. Three: assuming a syringe is U-100 when it is not.
All three are solved by the same two habits — do the arithmetic before the water goes in, and write the result on the glass. Neither costs anything and between them they cover almost every question this board gets.
This. Showing the working is the fastest way for somebody else to spot the mistake.
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.
Adding more water does not change how much peptide is in the vial. It changes the concentration, which changes the volume you draw for the same amount. That is the entire relationship.
- 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