pete_manc_UK said:Do it in two steps and it stops being confusing.
I am going to disagree with reconstituting low as a general rule. More diluent, more punctures, more in-use days at room temperature, and the stability trade-off is real. Precision is not the only variable being optimised.
If somebody has the primary source to hand I would rather cite it than paraphrase it.
LarryQC_SD said:Two of us with identical vials and identical diluent arrived at different unit counts, which means one of us has a conceptual error rather than a…
Bacteriostatic water quality matters for dosing arithmetic reconstitution. Not all BAC water is created equal:
- Should contain 0.9% benzyl alcohol as preservative
- Must be sterile and pyrogen-free
- Should come in a sealed, intact vial
- Check expiration date — yes, BAC water expires
- Store at room temperature, protected from light
I buy from a reputable medical supply company, not Amazon marketplace sellers. The $3 savings isn't worth the infection risk from unverified BAC water.
Dr.AddMedPHL said:I am going to disagree with reconstituting low as a general rule.
Compounding pharmacy dose accuracy check for dosing arithmetic: I always verify my first dose from a new vial by weighing it on a milligram scale. Draw up your dose, weigh the syringe, subtract empty syringe weight, compare to expected water weight at that volume.
For a 10-unit dose (0.1mL): expected weight ~100mg of water. If it's significantly off, your syringe may be inaccurate. Cheap insulin syringes can have ±5% volume accuracy. Spring for quality brands like BD or Terumo.
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Est. 1998. The synthesis house behind the vials you send for testing. ISO 9001 and cGMP certified, 1,500+ staff, batch-specific COA with every order.
Browse GL BiochemA narrower follow-up, since the general answer is now clear:
How to check the arithmetic without trusting a website calculator, since three calculators gave me three answers?
Closing the loop on my own question.
My error was treating units as a mass. Once I wrote mg/ml on the vial in marker and worked in millilitres first, the two of us got the same answer.