mike.trainer_LA 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.
One concrete data point for the thread. Practical: unopened, refrigerated at 2 to 8°C; in use, refrigerated and used within the preservative-limited window; never frozen; and a visual check every time — a haze that does not settle is a reason to stop, not to wonder.
Worth separating that from storage and cold chain, which this thread keeps folding into the same question. They behave differently and the advice does not transfer.
JessicaH_TX said:I am going to disagree with reconstituting low as a general rule.
Adding the part of the answer the thread has not reached. The distinction that matters is unopened versus in use. Unopened vials are stable refrigerated for their labelled shelf life and tolerate a limited excursion to room temperature. Once reconstituted, the clock is much shorter and is set by the preservative rather than by the peptide — bacteriostatic water's benzyl alcohol is what buys you multiple draws over weeks. Sterile water has no preservative and turns a multi-dose vial into a single-use one.
Worth separating that from storage and cold chain, which this thread keeps folding into the same question. They behave differently and the advice does not transfer.
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Browse GL BiochemA narrower follow-up, since the general answer is now clear:
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?
OP back with an update, since a thread like this is useless without one.
Resolved. I wrote mg, ml and mg/ml on the vial in marker and did the division in that order, and the two of us now get the same number every time.