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c/reconstitution·posted 2 years ago by u/gradient_goblin

[Discussion] can we stop arguing about units until somebody posts a number

Discussion Clean Column ×8 Slow Clap ×1 Receipts ×3

Trying to settle this properly because the thread from last year went in circles.

The claim: mg/mL matters. The counter-claim: it is measurement error. Both sides have been asserting it confidently for about 7 months without either producing anything.

What would actually settle it is 7 people measuring the same thing the same way. I have started; my numbers are below. They lean one way but not strongly enough for me to declare victory.

If you have data, post the data. If you have an opinion, flair it as an opinion.

3,961 up / 1,098 down78% upvoted55 commentsid 1g7sb411 Sep 2023

55 comments

30 in this archive, depth 5

best — the order this archive was captured in

u/units_not_mgMOD384 points·2 years ago

Flair changed to match the content. Read the sidebar before posting next time and we are square.

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u/iman_falk114 points·2 years ago·edited

never post a calculation as advice without stating the concentration

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[removed]84 points·2 years ago

[removed by moderator]

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u/ahmed_rasmussen52 points·2 years ago

more water means more units for the same dose, which means finer resolution

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u/gradient_goblinOP37 points·2 years ago

Show the arithmetic. Where did the units come from?

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u/anya_antonsen-26 points·2 years ago

more water means more units for the same dose, which means finer resolution

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u/georgi_adebayo274 points·2 years ago

Cosigning. The concentration on the vial in marker is load-bearing.

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u/ledger_modmod · vetting179 points·2 years ago

Cosigning.

Counter-anecdote: opposite result, same dose. Which mostly tells us the variance is huge.

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u/aurel_boateng130 points·2 years ago

Is that 5mg vial or 5mg?

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u/sleep_apnea_sam168 points·2 years ago
it is in the wiki actually
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u/britta_nakamura92 points·2 years ago

Cosigning. The concentration on the vial in marker is load-bearing.

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u/ines_lindqvist34 points·2 years ago

stopper coring on the 14th draw because you keep using the same entry point. rotate.

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u/elodie_grimaldi58 points·2 years ago

30mg vial, 2mL water, concentration is 30/2 — write it on the vial afterwards

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u/sofia_danquah36 points·2 years ago

the concentration on the vial in marker is the most important step

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u/janek_ferrari79 points·2 years ago

Cored the stopper on my 2th draw because I kept using the same entry point. Rotate the puncture site.

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u/gradient_goblinOP63 points·2 years ago·edited

Cored the stopper on my 2th draw because I kept using the same entry point.

Yes, exactly this, and it is the bit that took me 47 weeks to accept.

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u/yusuf_nakamura94 points·2 years ago·edited

u-100 syringe, not u-40, or your math is off by factor of 15

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u/tuva_kirchner45 points·2 years ago

Edit to your parent would help — the concentration you quoted assumes one scenario and you have written another above it.

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u/units_not_mgsyringe math21 points·2 years ago

This is correct. 2mL versus 17mL is the common mistake.

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u/sock_puppet_spotter80 points·2 years ago

Yeah, showing the arithmetic is the fastest way for someone to spot the error.

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u/anjali_tamm41 points·2 years ago

Cored the stopper on my 7th draw because I kept using the same entry point. Rotate the puncture site.

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u/gradient_goblinOP31 points·2 years ago

Reconstituted at 3mL when I meant 9mL. Caught it because the units looked wrong. Write the concentration.

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u/dilara_szabo21 points·2 years ago

never post a calculation as advice without stating the concentration

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u/quiet_reader_9933 points·2 years ago

The confident tone is doing a lot of work that the evidence is not.

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u/saskia_rahimi11 points·2 years ago

Cosigning. The concentration on the vial in marker is load-bearing.

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u/lyophile_lou20 points·2 years ago

dead space is real and the syringe matters

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u/liv_nkemelu31 points·2 years ago

This is correct. 1mL versus 5mL is the common mistake.

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u/spain_receta57 points·2 years ago

Disagree. What you are describing is consistent with concentration, not with what you concluded.

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u/viktor_erdogan24 points·2 years ago

Cosigning. The concentration on the vial in marker is load-bearing.

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u/yusuf_achebe17 points·2 years ago

Dead space ate 14 units on a low-volume draw. Tiny impact at 5mg, massive impact at 2.5mg.

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About c/reconstitution

The arithmetic and the technique. Bacteriostatic versus sterile water, reconstitution volume as a concentration choice, converting mg/mL into insulin-syringe units, dead space, swirl-not-shake, stopper coring, and how long a reconstituted vial is actually good for. Math errors get corrected fast and politely.

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