Reconstituting a multi-strength kit without mixing yourself up

Adding a note of thanks rather than an opinion. I did not know most of that.

Worth separating two things that post #12 runs together.

Preservative effectiveness is tested against a defined microbial challenge under defined conditions. It is not a licence to treat an entered vial as sterile indefinitely, and no supplier claims otherwise.

Adding it because I spent an afternoon working it out and nobody should have to twice.

What I would want before treating reconstituting a multi-strength kit as settled: the method, the sample, and whether anyone tried to find the opposite result. Two of the three are usually missing.

Reconstituting the whole vial when you will use a quarter of it is a decision to store the rest in solution, which is the least stable state it will ever be in. Sometimes that is the right trade and it should be a decision.

Post #18 answers the question as asked. The question underneath it is different.

I keep a log for reconstituting a multi-strength kit specifically because my memory of it turned out to be systematically wrong in one direction. Six weeks of notes cost nothing and settled it.

Reconstituting a multi-strength kit: if a kit contains 5 mg, 10 mg, 15 mg vials and you are reconstituting all of them, writing the concentration on each vial in permanent marker as you go is the single most useful thing you can do to avoid dose errors later.

This is the sort of thing that ought to be settled and apparently is not.

Reconstituting a multi-strength kit is one of those subjects where the general answer and the answer for a specific case diverge, and the thread will go in circles until someone says which one is being asked for.

I read post #21 twice before replying, because I had assumed the opposite.

Two things can be true about reconstituting a multi-strength kit at once: the mechanism is plausible and the evidence for the size of the effect is thin. Most of the argument here is people defending the first against attacks on the second.

This follows post #21 rather than contradicting it.

Preservative effectiveness is tested against a defined microbial challenge under defined conditions. It is not a licence to treat an entered vial as sterile indefinitely, and no supplier claims otherwise.

Adding the boring version of reconstituting a multi-strength kit, because the interesting version keeps getting posted and the boring one is usually right.

Check the ordinary explanations, in order, and stop when one of them accounts for what you are seeing. Most of the time the second one does.

Before the thread moves on from reconstituting a multi-strength kit — what is the sample size behind the claim? I am not being difficult; I have seen the same figure quoted from an n of four and from an n of four hundred.

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.

A guess, clearly labelled as one.

That is a fair summary of where the discussion has got to.

Worth separating two things that post #25 runs together.

Preservative effectiveness is tested against a defined microbial challenge under defined conditions. It is not a licence to treat an entered vial as sterile indefinitely, and no supplier claims otherwise.

Thank you for taking the time. That was more work than a reply usually is.