do units actually matter or is it forum lore at this point
Asking properly rather than in a comment on somebody else’s thread: do units actually matter or is it forum lore at this point.
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.
Reconstituted at 1mL when I meant to use a different volume. Caught it because the units looked wrong on the barrel. Now I write 30mg/mL on the glass before I put the cap back.
I keep a laminated card in the drawer with the arithmetic on it. Looks ridiculous. Has never once let me draw the wrong volume.
Sceptical readings welcome. The confident ones are the ones I distrust.
best — the order this archive was captured in
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.
Left up and flaired Explainer — the numbers in this one check out.
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.
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.
Show the arithmetic — where did the unit figure come from?
more water is not more drug, it is the same drug in a bigger volume
That is sterile water, not bacteriostatic. Same appearance, different product, and it matters for a multi-draw vial.
Started reconstituting everything to a round concentration and the six-in-the-morning error rate went to zero.
twice as much water halves the concentration and doubles the units for the same dose
dead space in the needle hub is real and it is small
reconstituting at a round concentration makes every later dose easy
reconstituting at a round concentration makes every later dose easy
Adding one thing — put the date on the label too. Concentration plus date and you can never mix two vials up.
units are a volume on a U-100 syringe, not a dose
Correction: that gives 30 units, not what you have written. 10mg into 3mL is 3.33mg/mL and the division follows from there.
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.
5mg into 1mL is 5mg/mL, and 0.75mg of that is 15 units
Cosigning the round-number approach. Reconstituting to something awkward is how you end up drawing 27.5 units at six in the morning.
the number you write down is the number you will trust at 6am
That only works if the fill weight is exactly the label weight, and it usually is not exactly anything.
How many mg in the vial and how many mL are you adding?
do the arithmetic before you reconstitute, not while holding a syringe
Right — the volume you add is the only variable you control here, and the cake does not change it meaningfully.
Right — the volume you add is the only variable you control here, and the cake does not change it meaningfully.
This is the sentence that makes the rest unnecessary. Write it on the vial and the problem is gone.
a U-100 syringe reads 100 units to the millilitre, every time
the powder cake sits at the bottom, the volume you add is the volume that counts
the powder cake sits at the bottom, the volume you add is the volume that counts
Disagreeing with this line only: adding more water is not a safety margin, it is a different divisor.
if the maths gives you a fraction of a unit, change the concentration
Pushback on the syringe advice: a U-100 barrel reads units of volume. Calling them "doses" is how the confusion starts.
- 1reconstituting at a round concentration makes every later dose easy10 comments in this branch · started by u/marta_weiss
- 2Right — the volume you add is the only variable you control here, and the…7 comments in this branch · started by u/alcohol_aversion