[Meta] the units rule is doing its job and people should stop complaining
the units rule is doing its job and people should stop complaining. Short post, long comment section, probably.
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.
I keep a laminated card in the drawer with the arithmetic on it. Looks ridiculous. Has never once let me draw the wrong volume.
Spent 9 weeks confused about this until somebody drew the table for me. 15mg, 3mL, 5mg/mL, 2.5mg is 50 units. That is the whole thing.
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.
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Is that a U-100 syringe? The barrel markings change the answer completely.
Are you accounting for the powder volume, or is that where the confusion is?
Bacteriostatic or plain sterile water?
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 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.
Disagree with the "more water is safer" framing. It is not safer, it is just a different number to divide by.
Not quite. Bacteriostatic and sterile water are not interchangeable for a multi-draw vial, and the difference is the preservative.
Agreed on the swirl. There is no reason to shake it and a good reason not to.
Agreed on the swirl.
Right, and the arithmetic behind it: 15mg in 3mL is 5mg/mL, so 0.5mg is 10 units.
Wrote the date on the vial as well as the concentration after losing track of which one was opened first.
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.
- 1Not quite. Bacteriostatic and sterile water are not interchangeable for a…6 comments in this branch · started by u/ledger_mod