unpopular opinion: most of what gets said here about reconstitution is guesswork
unpopular opinion: most of what gets said here about reconstitution is guesswork — a position I have arrived at slowly and would like tested.
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.
Not medical advice, obviously, and nothing here is approved for human use. One person with a spreadsheet.
best — the order this archive was captured in
a U-100 syringe reads 100 units to the millilitre, every time
a U-100 syringe reads 100 units to the millilitre, every time
This is the sentence that makes the rest unnecessary. Write it on the vial and the problem is gone.
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.
Careful — that arithmetic is wrong. 10mg in 2mL is 5mg/mL, so 1.5mg draws to 30 units, not what you wrote.
label the vial with the date as well as the concentration
Bacteriostatic water contains benzyl alcohol as a preservative, which is what makes repeated entry into the same vial reasonable.
viktor_kirchner has the units point exactly right. They are a volume on the barrel and nothing else.
viktor_kirchner has the units point exactly right.
Right, and the arithmetic behind it: 10mg in 1mL is 10mg/mL, so 2mg is 20 units.
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.
I would not round that figure. At 5mg/mL a rounding error of two units is a real fraction of the intended amount.
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 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.
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.
dead space in the needle hub is real and it is small
I keep a laminated card in the drawer with the arithmetic on it. Looks ridiculous. Has never once let me draw the wrong volume.
I keep a laminated card in the drawer with the arithmetic on it.
Disagreeing with this line only: adding more water is not a safety margin, it is a different divisor.
Not quite. Bacteriostatic and sterile water are not interchangeable for a multi-draw vial, and the difference is the preservative.
Asked KP what volume they reconstitute to for their own stability testing and they answered in one line. Useful thing to know.
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.
Did the maths give you a whole number of units, or a fraction?
reconstituting at a round concentration makes every later dose easy
the powder cake sits at the bottom, the volume you add is the volume that counts
units are a volume on a U-100 syringe, not a dose
Yes. Writing 5mg/mL on the vial takes four seconds and removes the entire class of error this board exists to fix.
bacteriostatic water has the preservative, sterile water does not
Spent 10 weeks confused about this until somebody drew the table for me. 20mg, 3mL, 6.67mg/mL, 5mg is 75 units. That is the whole thing.
Corrected the concentration in the title, which contradicted the body. Nothing else touched.
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.
Pushback on the syringe advice: a U-100 barrel reads units of volume. Calling them "doses" is how the confusion starts.
- 1I would not round that figure. At 5mg/mL a rounding error of two units is a…12 comments in this branch · started by u/hedda_ekstrom
- 2units are a volume on a U-100 syringe, not a dose6 comments in this branch · started by u/elin_ferrari