reconstituted at 1mL instead of 2mL and caught it before injecting. lucky.
reconstituted at 1mL instead of 2mL and caught it before injecting. lucky. It is the sort of thing everyone half-believes and nobody writes down.
The relevant figures are 1mL and 2mL, and they come from the same log I have kept the whole time.
Asked SSA what volume they reconstitute to for their own stability testing and they answered in one line. Useful thing to know.
Why "more water" keeps confusing people, including me for a month.
The vial contains a fixed amount of peptide. Water changes nothing about that amount. What it changes is concentration, and concentration is the divisor between the dose you want and the volume you draw.
So doubling the water halves the concentration and doubles the units for the same dose. Nothing is diluted in any sense that matters; you are simply reading a bigger number off the same barrel. Pick the water volume that puts your usual dose on a whole number of units and life gets easier.
Ask me anything specific. Anything general I will probably get wrong.
best — the order this archive was captured in
Adding more water does not change how much peptide is in the vial. It changes the concentration, which changes the volume you draw for the same amount. That is the entire relationship.
do the arithmetic before you reconstitute, not while holding a syringe
How many mg in the vial and how many mL are you adding?
Careful — that arithmetic is wrong. 5mg in 3mL is 1.67mg/mL, so 0.75mg draws to 45 units, not what you wrote.
bacteriostatic water has the preservative, sterile water does not
Research-use-only material is not approved for human use, so treat everything in this thread as arithmetic about solutions rather than instructions for a person.
What is written on the vial right now?
Small fix — a U-100 syringe is 100 units per mL. If yours is marked differently it is not U-100 and the whole calculation changes.
units are a volume on a U-100 syringe, not a dose
Spent 20 weeks confused about this until somebody drew the table for me. 5mg, 3mL, 1.67mg/mL, 1.5mg is 90 units. That is the whole thing.
Started reconstituting everything to a round concentration and the six-in-the-morning error rate went to zero.
That only works if the fill weight is exactly the label weight, and it usually is not exactly anything.
I would not round that figure. At 5mg/mL a rounding error of two units is a real fraction of the intended amount.
I would not round that figure.
This is the sentence that makes the rest unnecessary. Write it on the vial and the problem is gone.
Correction: that gives 30 units, not what you have written. 5mg into 2mL is 2.5mg/mL and the division follows from there.
The lyophilised cake displaces a small volume, so the true concentration is very slightly lower than the arithmetic suggests. It is a fraction of a percent and it is dwarfed by fill tolerance.
aim the stream at the glass wall, not at the cake
write the concentration on the vial in marker, that is the whole post
Reminder: this board does maths, not dosing. Nobody here tells another member what amount to take.
the number you write down is the number you will trust at 6am
Reconstituted at 2mL when I meant to use a different volume. Caught it because the units looked wrong on the barrel. Now I write 10mg/mL on the glass before I put the cap back.
The arithmetic in full: concentration is mass over volume, so 30mg into 2mL gives 15mg/mL. A U-100 syringe is graduated at 100 units per millilitre, so 1.5mg is 1.5 divided by 15 millilitres, which is 10 units.
That is sterile water, not bacteriostatic. Same appearance, different product, and it matters for a multi-draw vial.
if the maths gives you a fraction of a unit, change the concentration
Bacteriostatic or plain sterile water?
Show the arithmetic — where did the unit figure come from?
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Is that a U-100 syringe? The barrel markings change the answer completely.
Not quite. Bacteriostatic and sterile water are not interchangeable for a multi-draw vial, and the difference is the preservative.
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