Practice · Reconstitution

A 10 mg vial reconstituted three different ways, compared — the long version

Practice › Reconstitution reconstitution syringe units worked example concentration maths

j.moreauTL210 Jan 2025#1

A 10 mg vial reconstituted three different ways, compared — the long version — setting out what I have, and where I think it stops being reliable.

Asking about 10 mg vial reconstituted three directly, because I have read four threads on it and each answered a slightly different question.

The version I want answered is the narrow one: given the method stated below, is the result within what anyone else has seen? I am not asking what it means yet.

Method, numbers and the two assumptions I am aware of making are below. If the assumptions are wrong that is more useful to me than agreement.

17 likes 19mo

b.teixeiraTL215 Jan 2025#2

The confident answers on 10 mg vial reconstituted three and the well-sourced answers are not the same answers, which is the most useful thing I have learned reading this category.

2 likes 18mo

e.dalgleishTL3Regular19 Jan 2025#3

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.

I am reporting what happened, not recommending it.

0 likes 18mo

ar.kravchenkoTL223 Jan 2025#4

Add the diluent down the side of the vial rather than directly onto the cake. It is slower and it avoids the foaming that makes people think something has gone wrong.

28 likes 18mo

s.grahameTL227 Jan 2025#5

Collapsed as off-topic by two members at trust level 3 or above

Two things can be true about 10 mg vial reconstituted three 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.

e.roosTL230 Jan 2025#6

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.

Speaking for myself and not for anyone else who has posted here.

5 likes 18mo

citation_indexTL2Member2 Feb 2025 · edited#7

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.

0 likes 18mo

a.kravchenkoTL25 Feb 2025#8

citation_index, post #7: 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. Go to post

This follows post #7 rather than contradicting it.

10 mg vial reconstituted three 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.

0 likes in reply to #7 18mo

BirkelandTL3Regular8 Feb 2025#9

a.kravchenko, post #8: This follows post #7 rather than contradicting it. 10 mg vial reconstituted three 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. Go to post

No disagreement from me. Posting only so the question does not look ignored.

2 likes in reply to #8 18mo

v.rautioTL211 Feb 2025#10

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.

0 likes in reply to #7 18mo

sourced_claimsTL3Regular13 Feb 2025 · edited#11

Confirming post #8 from a second method, which matters more than confirming it from a second person.

Concentration is total mass divided by total volume, and everything else follows from that. Ten milligrams into two millilitres is five milligrams per millilitre, and it does not matter how the vial was labelled before you added anything.

I would be glad to be shown a cleaner way of putting this.

11 likes 17mo

r.bruunTL216 Feb 2025#12

Saving this. It is the version I will quote when the question comes round again.

24 likes in reply to #8 17mo

dr.villanuevaTL3Physician19 Feb 2025#13

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 the burden of proof on the interesting explanation, not the dull one.

0 likes 17mo

s.grimaldiTL221 Feb 2025#14

What I want from this 10 mg vial reconstituted three thread is the list of things that would need to be true for the claim to hold. If we can write that list, we can check it.

1 like 17mo

s.chowdhuryTL3Regular24 Feb 2025#15

Post #13 is the version of this I will quote in future. One addition.

Two questions I would want answered before drawing anything from the 10 mg vial reconstituted three data above: how were the cases selected, and what happened to the ones that dropped out.

17 likes 17mo

a.adeyemiTL226 Feb 2025#16

v.rautio, post #10: 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. Go to post

Where I part company with post #14, and it is a narrow parting.

A vial that will not fully dissolve: check in order: is the diluent genuinely room temperature (some preservatives crystallise in cold), is the vial being warmed gently rather than shaken hard, is the injection technique clean, is the vial integrity intact. Work through that checklist before concluding the powder is insoluble.

That is one dataset and I would not build a rule on it.

33 likes in reply to #10 17mo

h.oyelowoTL2Regular1 Mar 2025#17

10 mg vial reconstituted three: I have looked for the primary source twice and failed twice. Either it does not exist or it is somewhere I do not know to look, and I would like to know which.

0 likes 17mo

m.radichTL23 Mar 2025#18

Careful with the language on 10 mg vial reconstituted three. "Not detected" and "not present" are different findings and the first is a statement about the method.

3 likes 17mo

a.reyesTL4 Admin5 Mar 2025#19

j.moreau, post #1: A 10 mg vial reconstituted three different ways, compared — the long version — setting out what I have, and where I think it stops being reliable. Asking about 10 mg vial reconstituted three directly, because I have read four threads on it and each answered a slightly different question. The version I want answered is the narrow one:… Go to post

Reading rather than answering, but this is the post I would point somebody at.

4 likes in reply to #1 17mo

k.dahlbergTL28 Mar 2025 · edited#20

s.grahame, post #5: Two things can be true about 10 mg vial reconstituted three 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. Go to post

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.

12 likes in reply to #5 17mo

e.kimaniTL210 Mar 2025 · edited#21

Where I part company with post #20, and it is a narrow parting.

Two people can read the same figure differently here and both be reasonable.

0 likes 17mo

KnowltonTL3Regular12 Mar 2025#22

Bookmarking this. I will come back when I have something worth adding.

27 likes 17mo

i.brobergTL215 Mar 2025#23

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.

Take it as a starting point and not as a specification.

8 likes 16mo

VThorvaldsenTL3Regular17 Mar 2025#24

Knowlton, post #22: Bookmarking this. I will come back when I have something worth adding. Go to post

Adding the measurement that post #23 says would settle it.

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.

Someone should write this up properly, and it should probably not be me.

2 likes in reply to #22 16mo

i.rasmussenTL219 Mar 2025#25

Post #23 put the caveat in the right place and I want to underline it.

What would change my mind on 10 mg vial reconstituted three is a second dataset collected by someone with no stake in the first. Until then I hold it loosely and I would rather say so than pretend to more.

0 likes 16mo

MSaarinenTL3Regular22 Mar 2025#26

Post #23 is the version of this I will quote in future. One addition.

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.

One more caveat and then I will stop qualifying: the sample selected itself.

20 likes 16mo

e.krastevTL224 Mar 2025#27

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.

5 likes 16mo

s.poulsenTL3Regular26 Mar 2025#28

Knowlton, post #22: Bookmarking this. I will come back when I have something worth adding. Go to post

On 10 mg vial reconstituted three, the part that usually goes wrong is that the question is asked as though it has one answer. It has a range, and the width of the range is the interesting bit.

If you can post the two or three numbers you are working from, several people here will check the arithmetic rather than argue about the conclusion.

0 likes in reply to #22 16mo

KLindqvistTL4 Moderator28 Mar 2025#29

sourced_claims, post #11: Confirming post #8 from a second method, which matters more than confirming it from a second person. Concentration is total mass divided by total volume, and everything else follows from that. Ten milligrams into two millilitres is five milligrams per millilitre, and it does not matter how the vial was labelled before you added… Go to post

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.

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

28 likes in reply to #11 16mo

a.ibarraTL230 Mar 2025 · edited#30

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.

Happy to be the one who is wrong here if it settles the question.

14 likes 16mo

Sponsored Sigma-Aldrich — certified reference materialsReference standards, analytical reagents and certified materials for method calibration. If you are validating a method, this is where the standard comes from.Reference standards →