[Discussion] the reconstitution advice in here is 3 years out of date
the reconstitution advice in here is 3 years out of date, and I am aware this is a minority view on this board.
3 years. Those are measured, not estimated, and not rounded up in my favour.
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.
That is everything I have. The rest is opinion and I have tried to keep it out.
best — the order this archive was captured in
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.
Spent 4 weeks confused about this until somebody drew the table for me. 5mg, 3mL, 1.67mg/mL, 0.5mg is 30 units. That is the whole thing.
How many mg in the vial and how many mL are you adding?
Wrote the date on the vial as well as the concentration after losing track of which one was opened first.
Left up and flaired Explainer — the numbers in this one check out.
write the concentration on the vial in marker, that is the whole post
Wrote the date on the vial as well as the concentration after losing track of which one was opened first.
Disagreeing with this line only: adding more water is not a safety margin, it is a different divisor.
I keep a laminated card in the drawer with the arithmetic on it. Looks ridiculous. Has never once let me draw the wrong volume.
Reconstituted at 3mL when I meant to use a different volume. Caught it because the units looked wrong on the barrel. Now I write 5mg/mL on the glass before I put the cap back.
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.
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.
Pushback on the syringe advice: a U-100 barrel reads units of volume. Calling them "doses" is how the confusion starts.
That is sterile water, not bacteriostatic. Same appearance, different product, and it matters for a multi-draw vial.
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 5mg is 5 divided by 10 millilitres, which is 50 units.
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.
Correcting myself above: I wrote the concentration the wrong way up. Mass over volume, not volume over mass.
more water is not more drug, it is the same drug in a bigger volume
more water is not more drug, it is the same drug in a bigger volume
ahmed_rasmussen has the units point exactly right. They are a volume on the barrel and nothing else.
Careful — that arithmetic is wrong. 5mg in 2mL is 2.5mg/mL, so 1mg draws to 40 units, not what you wrote.
units are a volume on a U-100 syringe, not a dose
The arithmetic in full: concentration is mass over volume, so 20mg into 2mL gives 10mg/mL.
Right, and the arithmetic behind it: 15mg in 3mL is 5mg/mL, so 0.75mg is 15 units.
- 1The arithmetic in full: concentration is mass over volume, so 20mg into 2mL…8 comments in this branch · started by u/britta_nakamura