This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
Everything in post #59 holds. The case it does not cover is the one I have.
Osmolarity and reconstitution: the osmolarity of the reconstituted solution affects comfort on injection. Isotonic solutions (close to blood osmolarity) are less irritating than hypertonic solutions. This is why diluent choice (sterile water vs. saline) matters.
Write the reconstitution date and the concentration on the vial. Not on a note, on the vial. Every account here of a dosing error involving the wrong concentration involves a vial with nothing written on it.
I would treat that as a working assumption and revisit it.
Arithmetic step by step: a 5 mg vial with 2 mL of diluent gives (5 mg) / (2 mL) = 2.5 mg/mL. On a U-100 syringe at that concentration, 100 units = 1 mL = 2.5 mg, so each unit = 0.025 mg. A 0.25 mg dose = 0.25 / 0.025 = 10 units. Different concentration: different arithmetic, same principle.
Noting that the question and the thing people usually mean by it are different.
Building on post #63 rather than restating it.
I would keep 10 mg vial reconstituted three and the decision it usually gets used for separate in this thread. They are related and they are not the same question, and merging them is why the last one went badly.
Trying to state the 10 mg vial reconstituted three position in a way that someone who disagrees would recognise as fair, because I do not think the version in this thread passes that test.
Why "add 2 mL" is not an instruction: the powder in the vial takes up space. "Add 2 mL to a 10 mL vial" and "add 2 mL of diluent so the final volume is approximately 2 mL" are different instructions. Stating the final target volume is clearer than stating the diluent added.
I would rather be precise about what I do not know than vague about what I do.
Where I part company with post #63, and it is a narrow parting.
A 10 mg vial reconstituted three different ways: 1 mL diluent gives 10 mg/mL, 2 mL gives 5 mg/mL, 4 mL gives roughly 2.5 mg/mL. The arithmetic is the same; the concentration determines which syringe graduations are legible.
Post #67 is the version of this I will quote in future. One addition.
Swirling versus inverting versus leaving it alone: the vial can be gently warmed (hands around it) and swirled with a rolling motion. Vigorous shaking introduces air and can denature the peptide. Leaving it alone at room temperature usually works given enough time.
Posting my 10 mg vial reconstituted three numbers with the method attached so they can be discounted properly. Uncontrolled, unblinded, and collected by someone who wanted a particular answer.
How much of the diluent volume the powder itself displaces: for a small peptide vial, the powder volume is negligible. For a larger vial or a kit with multiple compounds, the displacement can be a few tenths of a millilitre. If precision matters to you, account for it by targeting a final weight rather than a final volume.
Agreed, and I will stop repeating the version of this I had been repeating.
Narrowing post #70, because the general version has more than one answer.
Small correction to my own earlier position on 10 mg vial reconstituted three. I had the units the wrong way round, which changes the conclusion by an order of magnitude and therefore changes it entirely.
Everything in post #73 holds. The case it does not cover is the one I have.
The question underneath 10 mg vial reconstituted three is usually "how would I tell?" rather than "what is true?", and that one has a method attached to it.
Write down what you would expect to see under each hypothesis before you collect anything. If they predict the same observation, collecting it will not help.
Do not shake. Swirl, or leave it. Vigorous agitation introduces air and shear, and neither helps a peptide go into solution any faster than patience does.
Post #75 answers the question as asked. The question underneath it is different.
Answering the 10 mg vial reconstituted three question as asked, then the question I think is meant. As asked: yes, with the qualification below. As meant: it depends on how the first measurement was taken.
How much of the diluent volume the powder itself displaces: for a small peptide vial, the powder volume is negligible. For a larger vial or a kit with multiple compounds, the displacement can be a few tenths of a millilitre. If precision matters to you, account for it by targeting a final weight rather than a final volume.
Worth separating two things that post #76 runs together.
Why "add 2 mL" is not an instruction: the powder in the vial takes up space. "Add 2 mL to a 10 mL vial" and "add 2 mL of diluent so the final volume is approximately 2 mL" are different instructions. Stating the final target volume is clearer than stating the diluent added.
It is worth checking rather than assuming, which costs nothing.
Everything in post #77 holds. The case it does not cover is the one I have.
Checked the 10 mg vial reconstituted three claim against the primary source this morning. It survives, with a narrower scope than the version quoted here. Posting the narrower scope.
Filter needles are worth considering if you are drawing from a glass ampoule and are pointless overhead for a stoppered vial. The trade is dead volume against particulate risk.
Two sources, same conclusion, and I could not rule out that one copied the other.
A 10 mg vial reconstituted three different ways: 1 mL diluent gives 10 mg/mL, 2 mL gives 5 mg/mL, 4 mL gives roughly 2.5 mg/mL. The arithmetic is the same; the concentration determines which syringe graduations are legible.
I would hold that lightly until someone with a larger sample weighs in.
I read post #81 twice before replying, because I had assumed the opposite.
Swirling versus inverting versus leaving it alone: the vial can be gently warmed (hands around it) and swirled with a rolling motion. Vigorous shaking introduces air and can denature the peptide. Leaving it alone at room temperature usually works given enough time.
Since 10 mg vial reconstituted three keeps coming up, it should probably be a maintained page rather than a recurring thread. I am happy to draft it if someone with more direct experience will review it.
Write the reconstitution date and the concentration on the vial. Not on a note, on the vial. Every account here of a dosing error involving the wrong concentration involves a vial with nothing written on it.
A guess, clearly labelled as one.
Arithmetic step by step: a 5 mg vial with 2 mL of diluent gives (5 mg) / (2 mL) = 2.5 mg/mL. On a U-100 syringe at that concentration, 100 units = 1 mL = 2.5 mg, so each unit = 0.025 mg. A 0.25 mg dose = 0.25 / 0.025 = 10 units. Different concentration: different arithmetic, same principle.
I would not lead a decision with this, but I would not ignore it either.
This settles it for me, at least until somebody posts a reason it should not.
Two people can reconstitute the same vial to different concentrations and both be right. The dose is the same; only the volume drawn differs. This confuses more discussions here than any other single point.
The uncertainty is in the assumption, not in the calculation.