bacteriostatic water is the most under-discussed thing on this board
bacteriostatic water is the most under-discussed thing on this board. Not a hot take, just something I have not seen said plainly here.
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.
Tell me where this is wrong. That is the useful part of posting it.
best — the order this archive was captured in
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.
units are a volume on a U-100 syringe, not a dose
The arithmetic in full: concentration is mass over volume, so 5mg into 1mL gives 5mg/mL. A U-100 syringe is graduated at 100 units per millilitre, so 2mg is 2 divided by 5 millilitres, which is 40 units.
Agreed — units are volume. Once that lands, the rest of the arithmetic is one division.
[removed by moderator]
label the vial with the date as well as the concentration
I keep a laminated card in the drawer with the arithmetic on it. Looks ridiculous. Has never once let me draw the wrong volume.
Bacteriostatic or plain sterile water?
swirl, never shake
Pushback on the syringe advice: a U-100 barrel reads units of volume. Calling them "doses" is how the confusion starts.
write the concentration on the vial in marker, that is the whole post
Right — the volume you add is the only variable you control here, and the cake does not change it meaningfully.
Agreed on the swirl. There is no reason to shake it and a good reason not to.
I would not round that figure. At 5mg/mL a rounding error of two units is a real fraction of the intended amount.
The whole calculation, once, with real numbers.
You have a 20mg vial. You add 3mL of bacteriostatic water. Concentration is mass over volume: 6.67mg/mL. A U-100 insulin syringe is graduated at 100 units per millilitre, so one unit is 0.01mL.
To draw 5mg you need 5 divided by 6.67 millilitres, which is 75 units on the barrel. Write "6.67mg/mL" on the vial in marker before you put it away, and you never have to do this again for that vial.
Cosigning the round-number approach. Reconstituting to something awkward is how you end up drawing 27.5 units at six in the morning.
aim the stream at the glass wall, not at the cake
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.
dead space in the needle hub is real and it is small
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.
This is the sentence that makes the rest unnecessary.
Adding one thing — put the date on the label too. Concentration plus date and you can never mix two vials up.
Yes. Writing 5mg/mL on the vial takes four seconds and removes the entire class of error this board exists to fix.
- 1swirl, never shake7 comments in this branch · started by u/julia_erdogan
- 2aim the stream at the glass wall, not at the cake7 comments in this branch · started by u/saskia_mwangi