someone explain concentration to me like I have not read a paper in years
Asking properly rather than in a comment on somebody else’s thread: someone explain concentration to me like I have not read a paper in years.
Shook the first vial because nobody told me not to. It was fine, but I have swirled every one since.
Wrote the date on the vial as well as the concentration after losing track of which one was opened first.
Started reconstituting everything to a round concentration and the six-in-the-morning error rate went to zero.
Ask me anything specific. Anything general I will probably get wrong.
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.
Asked QYB what volume they reconstitute to for their own stability testing and they answered in one line. Useful thing to know.
Are you accounting for the powder volume, or is that where the confusion is?
Agreed on the swirl. There is no reason to shake it and a good reason not to.
That is sterile water, not bacteriostatic. Same appearance, different product, and it matters for a multi-draw vial.
Corrected the concentration in the title, which contradicted the body. Nothing else touched.
Pushback on the syringe advice: a U-100 barrel reads units of volume. Calling them "doses" is how the confusion starts.
dead space in the needle hub is real and it is small
dead space in the needle hub is real and it is small
Adding one thing — put the date on the label too. Concentration plus date and you can never mix two vials up.
a U-100 syringe reads 100 units to the millilitre, every time
This. Showing the working is the fastest way for somebody else to spot the mistake.
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.
the number you write down is the number you will trust at 6am
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.
Show the arithmetic — where did the unit figure come from?
What concentration did you actually reconstitute at, rather than what did you intend to?
units are a volume on a U-100 syringe, not a dose
the powder cake sits at the bottom, the volume you add is the volume that counts
aim the stream at the glass wall, not at the cake
units are a volume on a U-100 syringe, not a dose
Right, and the arithmetic behind it: 5mg in 1mL is 5mg/mL, so 1.5mg is 30 units.
label the vial with the date as well as the concentration
bacteriostatic water has the preservative, sterile water does not
reconstituting at a round concentration makes every later dose easy
Yes, and the dead-space point is worth repeating: it is small, it is real, and it is the same for every draw.
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.
I keep a laminated card in the drawer with the arithmetic on it. Looks ridiculous. Has never once let me draw the wrong volume.
30mg into 2mL is 15mg/mL, and 0.75mg of that is 5 units
twice as much water halves the concentration and doubles the units for the same dose
if the maths gives you a fraction of a unit, change the concentration
- 1What concentration did you actually reconstitute at, rather than what did…8 comments in this branch · started by u/yusuf_achebe
- 2Corrected the concentration in the title, which contradicted the body.…6 comments in this branch · started by u/bac_water_bandit