Converting between mg/mL and units per dose, both directions — the long version

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.

Worked example, since the arithmetic is the whole question. Five milligrams into one millilitre is 5 mg/mL. A 0.25 mg dose is 0.05 mL, which is five units on a U-100 syringe. Check that against your own numbers rather than taking mine.

Building on post #18 rather than restating it.

The best check on any reconstitution calculation is to do it twice by two different routes — mass per volume, then volume per dose — and see whether they agree. They should, and when they do not it is nearly always the concentration step.

I would rather say I do not know than round it up to an answer.

Fine by me. I had wanted a stronger conclusion and there is not one available.

Dead volume is the part nobody mentions until it costs them a dose. A fixed-needle insulin syringe holds very little; a detachable-needle luer configuration can hold enough to matter at small doses.

It is worth stating the boring hypothesis before the interesting one.

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.

I would put this at better than even and not much better.

Adding thanks rather than a view. I do not have a view worth the space.

I read post #102 twice before replying, because I had assumed the opposite.

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.

The number is defensible. The precision I gave it is not.

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.

Adding the caveat now so it does not have to be extracted later.