[Discussion] can we stop arguing about mg/mL until somebody posts a number
can we stop arguing about mg/mL until somebody posts a number — that is what I am asking, and I have already read the wiki twice.
The failure modes I have actually seen posted here, in order of frequency.
One: reconstituting at a different volume than intended and not writing it down, so the next draw is based on a remembered concentration. Two: treating units as a dose rather than a volume, which breaks the moment the concentration changes. Three: assuming a syringe is U-100 when it is not.
All three are solved by the same two habits — do the arithmetic before the water goes in, and write the result on the glass. Neither costs anything and between them they cover almost every question this board gets.
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 1.5mg is 1.5 divided by 5 millilitres, which is 30 units.
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.
Happy to answer the boring questions. Those are usually the ones worth asking.
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.
Spent 20 weeks confused about this until somebody drew the table for me. 30mg, 1mL, 30mg/mL, 1.5mg is 5 units. That is the whole thing.
units are a volume on a U-100 syringe, not a dose
reconstituting at a round concentration makes every later dose easy
more water is not more drug, it is the same drug in a bigger volume
What concentration did you actually reconstitute at, rather than what did you intend to?
twice as much water halves the concentration and doubles the units for the same dose
twice as much water halves the concentration and doubles the units for the same dose
RetaAndRegret2 has the units point exactly right. They are a volume on the barrel and nothing else.
Corrected the concentration in the title, which contradicted the body. Nothing else touched.
That only works if the fill weight is exactly the label weight, and it usually is not exactly anything.
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the number you write down is the number you will trust at 6am
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.