[Meta] proposal — a flair for bacteriostatic water posts
Putting this to the board: proposal — a flair for bacteriostatic water posts.
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.
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.
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.
Would rather be corrected in public than confident in private.
best — the order this archive was captured in
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 2mg is 2 divided by 10 millilitres, which is 20 units.
Reminder: this board does maths, not dosing. Nobody here tells another member what amount to take.
I keep a laminated card in the drawer with the arithmetic on it. Looks ridiculous. Has never once let me draw the wrong volume.
Started reconstituting everything to a round concentration and the six-in-the-morning error rate went to zero.
This. Showing the working is the fastest way for somebody else to spot the mistake.
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.
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.
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.
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.
How many mg in the vial and how many mL are you adding?
What is written on the vial right now?
That only works if the fill weight is exactly the label weight, and it usually is not exactly anything.
Right — the volume you add is the only variable you control here, and the cake does not change it meaningfully.
That is sterile water, not bacteriostatic. Same appearance, different product, and it matters for a multi-draw vial.
Yes, and the dead-space point is worth repeating: it is small, it is real, and it is the same for every draw.
the powder cake sits at the bottom, the volume you add is the volume that counts
if the maths gives you a fraction of a unit, change the concentration
Reconstituted at 3mL 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.
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