[Explainer] why 1mL syringes cause overdoses and 0.3mL ones do not
why 1mL syringes cause overdoses and 0.3mL ones do not. If you already knew this, the post is not for you and you can scroll on.
1mL and 0.3mL. Those are measured, not estimated, and not rounded up in my favour.
Spent 17 weeks confused about this until somebody drew the table for me. 5mg, 1mL, 5mg/mL, 2mg is 40 units. That is the whole thing.
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.
Sceptical readings welcome. The confident ones are the ones I distrust.
best — the order this archive was captured in
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.
label the vial with the date as well as the concentration
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.
Wrote the date on the vial as well as the concentration after losing track of which one was opened first.
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.
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.
Started reconstituting everything to a round concentration and the six-in-the-morning error rate went to zero.
Shook the first vial because nobody told me not to. It was fine, but I have swirled every one since.
Is that a U-100 syringe? The barrel markings change the answer completely.
units are a volume on a U-100 syringe, not a dose
I would not round that figure. At 5mg/mL a rounding error of two units is a real fraction of the intended amount.
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.
If your calculation produces a fraction of a unit, the concentration is wrong for your dose.
Disagreeing with this line only: adding more water is not a safety margin, it is a different divisor.
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.
Disagreeing with this line only: adding more water is not a safety margin, it is a different divisor.
piotr_bruun has the units point exactly right. They are a volume on the barrel and nothing else.
dead space in the needle hub is real and it is small
Disagreeing with this line only: adding more water is not a safety margin, it is a different divisor.
Adding one thing — put the date on the label too. Concentration plus date and you can never mix two vials up.
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Show the arithmetic — where did the unit figure come from?
aim the stream at the glass wall, not at the cake
Left up and flaired Explainer — the numbers in this one check out.
Asked HJ what volume they reconstitute to for their own stability testing and they answered in one line. Useful thing to know.
twice as much water halves the concentration and doubles the units for the same dose
more water is not more drug, it is the same drug in a bigger volume
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.
more water is not more drug, it is the same drug in a bigger volume
This is the sentence that makes the rest unnecessary. Write it on the vial and the problem is gone.
This. Showing the working is the fastest way for somebody else to spot the mistake.
The arithmetic in full: concentration is mass over volume, so 5mg into 3mL gives 1.67mg/mL. A U-100 syringe is graduated at 100 units per millilitre, so 0.25mg is 0.25 divided by 1.67 millilitres, which is 15 units.
- 1If your calculation produces a fraction of a unit, the concentration is…8 comments in this branch · started by u/nadia_kjaer
- 2Asked HJ what volume they reconstitute to for their own stability testing…6 comments in this branch · started by u/marisol_frisk