[Meta] the dead space rule is doing its job and people should stop complaining
the dead space rule is doing its job and people should stop complaining. Comments open, and the wording is genuinely up for discussion.
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.
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.
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 0.5mg is 0.5 divided by 10 millilitres, which is 5 units.
Please do not ask me what dose you should be on. I genuinely do not know and neither does anyone else here.
best — the order this archive was captured in
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.
Wrote the date on the vial as well as the concentration after losing track of which one was opened first.
Asked Homopeptide what volume they reconstitute to for their own stability testing and they answered in one line. Useful thing to know.
Yes, and the dead-space point is worth repeating: it is small, it is real, and it is the same for every draw.
Left up and flaired Explainer — the numbers in this one check out.
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.
Is that a U-100 syringe? The barrel markings change the answer completely.
How many mg in the vial and how many mL are you adding?
That is sterile water, not bacteriostatic. Same appearance, different product, and it matters for a multi-draw vial.