Practice · Reconstitution

Why I now write the concentration on the vial in marker

Practice › Reconstitution syringe units bacteriostatic water concentration maths

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compounding_ruthTL4Pharmacist22 Jun 2026#1

Asking directly, because I could not find a straight answer: Why I now write the concentration on the vial in marker

Practical question with the units stated, because I have seen how quickly these go wrong without them.

I have a 15 mg vial of tirzepatide and I am working to a 5.0 mg step. My syringes are U-100 insulin syringes, 1.0 mL barrel.

I can do the arithmetic and I have done it twice, getting the same answer both times, but I would like someone to check the reasoning rather than the number — specifically whether I have thought about the residual volume correctly, and whether the graduation I am landing on is one a person can actually read.

1 like 1mo

an.ibarraTL2 Moderator29 Jun 2026#2

Coming back to the opening post, because the follow-up matters more than the original answer.

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.

4 likes 29d

TL4_HalvorsenTL4Leader · Journal club4 Jul 2026#3

compounding_ruth, post #1: Asking directly, because I could not find a straight answer: Why I now write the concentration on the vial in marker Practical question with the units stated, because I have seen how quickly these go wrong without them. I have a 15 mg vial of tirzepatide and I am working to a 5.0 mg step. My syringes are U-100 insulin syringes, 1.0 mL… Go to post

I disagree with the reply above, and I think the disagreement is substantive rather than terminological.

The distinction being drawn does not survive when you look at the published data for this specific question. I would be glad to be shown wrong on this, because the version I am arguing against is more convenient.

13 likes in reply to #1 24d

c.amankwahTL2 Moderator9 Jul 2026#4

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.

26 likes 19d

endo_fellow_rkTL313 Jul 2026#5

Post hidden by community flags

Staff rationale: Hidden by community flags. Described a research-use-only compound as approved for human use after a correction earlier in this topic (R4).

This follows post #2 rather than contradicting it.

Choosing a concentration on purpose rather than by accident: starting with "I want to draw 0.5 mL per dose" and working backward to the required concentration is more efficient than picking a diluent volume and hoping the math works out. State your target volume, then the required concentration follows.

The corresponding entry is in the public moderation log. Hidden posts are never deleted.

r.ekstromTL2 Moderator17 Jul 2026#6

I read post #4 twice before replying, because I had assumed the opposite.

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.

2 likes 11d

This topic was referenced in

Foaming during reconstitution and whether it mattersPractice › Reconstitution · 24 replies

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