[Discussion] the bacteriostatic water advice in here is 3 years out of date
the bacteriostatic water advice in here is 3 years out of date. Not a hot take, just something I have not seen said plainly here.
The numbers the title promised, since a headline without them is worthless: 3 years. Everything below is context for those.
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.
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.
Sceptical readings welcome. The confident ones are the ones I distrust.
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.
Show the arithmetic — where did the unit figure come from?
That only works if the fill weight is exactly the label weight, and it usually is not exactly anything.
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.
This. Showing the working is the fastest way for somebody else to spot the mistake.
I keep a laminated card in the drawer with the arithmetic on it. Looks ridiculous. Has never once let me draw the wrong volume.
How many mg in the vial and how many mL are you adding?
Did the maths give you a whole number of units, or a fraction?
Right — the volume you add is the only variable you control here, and the cake does not change it meaningfully.
Left up and flaired Explainer — the numbers in this one check out.
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.
Asked GGPeps what volume they reconstitute to for their own stability testing and they answered in one line. Useful thing to know.
Cosigning the round-number approach. Reconstituting to something awkward is how you end up drawing 27.5 units at six in the morning.
Same. I got this wrong once, caught it because the units looked absurd, and have written on every vial since.
the number you write down is the number you will trust at 6am
Correction: that gives 50 units, not what you have written. 30mg into 3mL is 10mg/mL and the division follows from there.
Yes. Writing 5mg/mL on the vial takes four seconds and removes the entire class of error this board exists to fix.
Pushback on the syringe advice: a U-100 barrel reads units of volume. Calling them "doses" is how the confusion starts.
units are a volume on a U-100 syringe, not a dose
What concentration did you actually reconstitute at, rather than what did you intend to?
What concentration did you actually reconstitute at, rather than what did you intend to?
This is the sentence that makes the rest unnecessary. Write it on the vial and the problem is gone.
more water is not more drug, it is the same drug in a bigger volume
- 1Adding more water does not change how much peptide is in the vial. It…7 comments in this branch · started by u/adaeze_cabrera
- 2Yes. Writing 5mg/mL on the vial takes four seconds and removes the entire…7 comments in this branch · started by u/kenji_kimani