This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.
Fine by me. I had wanted a stronger conclusion and there is not one available.
Worth separating two things that post #32 runs together.
Swirling until fully clear before drawing is worth the extra minute. A partially dissolved preparation is not uniform and the first dose out of it is not the same as the last.
I would be glad to be shown a cleaner way of putting this.
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.
I had written a reply contradicting post #34 and deleted it. Here is what survived.
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.
Picking up post #36: that is the part I would want checked first.
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 mechanism is plausible, which is not the same as established.
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 answer changed when I changed how I was measuring, which was informative.
Narrowing post #36, because the general version has more than one answer.
The decimal-point error: computing 5 mg / 2 mL as 0.25 mg/mL instead of 2.5 mg/mL is the most common arithmetic error in this subcategory. The habit that catches it: writing the units in every step of the calculation.
That has held every time I have looked, which is not the same as always.
Over-dilution: if your target dose is 0.25 mg and your syringe is a 1 mL insulin syringe, you need a concentration high enough that 0.25 mg fits on the scale. A 0.25 mg/mL solution requires drawing the entire 1 mL syringe — not readable. A 5 mg/mL solution requires drawing 50 μL — also not practical on an insulin syringe.
Anyone who has looked at this more carefully, please correct the record.
Clear enough that I do not think I have a follow-up, which is unusual.
The arithmetic in post #39 is right; the assumption feeding it is the part to check.
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.
Filing this under things that are true until someone shows me otherwise.
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.
Adding the measurement that post #43 says would settle it.
A 0.3 mL barrel has more space between graduations than a 1 mL barrel for the same volume, which is the entire practical argument for the smaller syringe. Resolution, not capacity.
The part I am sure of is shorter than the part I have written.
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.
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.
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.
The decimal-point error: computing 5 mg / 2 mL as 0.25 mg/mL instead of 2.5 mg/mL is the most common arithmetic error in this subcategory. The habit that catches it: writing the units in every step of the calculation.
Not disagreeing with anyone above, just adding the bit I keep having to look up.
Picking up post #50: that is the part I would want checked first.
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.
It is a small point and it changes the answer, which is an awkward combination.
On post #52 — agreed on the reasoning, with one qualification.
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.
Somebody will have a better source than mine, and I hope they post it.
Confirming post #54 from a second method, which matters more than confirming it from a second person.
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.
I have kept the units in throughout, for the obvious reason.
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.
That is a description of practice, not a recommendation of it.
Over-dilution: if your target dose is 0.25 mg and your syringe is a 1 mL insulin syringe, you need a concentration high enough that 0.25 mg fits on the scale. A 0.25 mg/mL solution requires drawing the entire 1 mL syringe — not readable. A 5 mg/mL solution requires drawing 50 μL — also not practical on an insulin syringe.
Post #56 describes the usual case. This is about the unusual one.
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.
Post #58 is the version of this I will quote in future. One addition.
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.
I had read the opposite somewhere and cannot now find where, which tells me something.