JennaRN said:Dead space is the answer to the missing dose.
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.
Dr.GastroMayo said:I reconstituted a 10mg vial with 2ml of bacteriostatic water and I want someone to check my unit arithmetic before I draw anything, because I keep…
Regarding dosing arithmetic multi-dose vial contamination prevention: after reconstituting, I wipe the vial stopper with a fresh alcohol swab before EVERY single draw. I also never touch the stopper with my fingers and use a new needle for each draw.
Even with bacteriostatic water preservative, contamination is cumulative. One sloppy draw can introduce bacteria that multiply over days. Aseptic technique isn't optional — it's essential for injectable medications.
Dr.CardioMD said:I am going to disagree with reconstituting low as a general rule.
Peptide calculator app recommendation for dosing arithmetic: I use PeptideCalc to calculate reconstitution volumes and injection doses. Eliminates math errors completely.
Input: vial size (mg), desired concentration (mg/mL), prescribed dose (mg)
Output: BAC water volume (mL), injection volume (units on insulin syringe)
A math error with injectable medication can mean underdosing or overdosing. Use a calculator every time until the math becomes second nature.
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Shop Reference StandardsFollowing on from CanadaChris — and this may be the naive question:
How much material I am losing to dead space, and whether that explains why a 10mg vial gives me nine usable draws rather than ten?
Reporting back.
Follow-up: it was dead space. Switching to a low-dead-space fixed-needle syringe gave me the tenth dose back.