unpopular opinion: most of what gets said here about units are guesswork
Posting this as a discussion rather than a claim: unpopular opinion: most of what gets said here about units are guesswork. Shook the first vial because nobody told me not to. It was fine, but I have swirled every one since. I keep a laminated card in the drawer with the arithmetic on it. Looks ridiculous. Has never…
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.
The arithmetic in full: concentration is mass over volume, so 10mg into 3mL gives 3.33mg/mL. A U-100 syringe is graduated at 100 units per millilitre, so 2.5mg is 2.5 divided by 3.33 millilitres, which is 75 units.
The arithmetic in full: concentration is mass over volume, so 10mg into 3mL gives 3.33mg/mL.
Right, and the arithmetic behind it: 5mg in 2mL is 2.5mg/mL, so 0.25mg is 10 units.
more water is not more drug, it is the same drug in a bigger volume
the powder cake sits at the bottom, the volume you add is the volume that counts
What concentration did you actually reconstitute at, rather than what did you intend to?