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.
The part I am sure of is shorter than the part I have written.
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.
I would rather be precise about what I do not know than vague about what I do.
Filter needles are worth considering if you are drawing from a glass ampoule and are pointless overhead for a stoppered vial. The trade is dead volume against particulate risk.
Reconstituting the whole vial when you will use a quarter of it is a decision to store the rest in solution, which is the least stable state it will ever be in. Sometimes that is the right trade and it should be a decision.
That holds under the stated conditions and I have stated them.
Read the full topic (17 posts)
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A 5 mg vial and a 0.25 mg dose: the arithmetic in full
A 5 mg vial and a 0.25 mg dose: the arithmetic in full Writing it up because I had to work it out twice and would rather nobody else did. 5 mg vial: setting out the arithmetic in full, because I have had to…
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+124 | 141 | 16k | 2d |
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Over-dilution: when your dose falls below one readable graduation
On the subject in the title: Over-dilution: when your dose falls below one readable graduation Working notes rather than a conclusion. I have read the maintained page on this and I still have a gap, so I am…
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+15 | 19 | 248 | 15mo |
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Coming back to: Reconstitution volumes that produce round numbers, tabulated
On the subject in the title: Reconstitution volumes that produce round numbers, tabulated Working notes rather than a conclusion. Writing this out with the numbers in it, because "roughly" is how these go…
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2 | 24k | 6mo | |
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Checking someone else's arithmetic: a worked example thread
Checking someone else's arithmetic: a worked example thread Writing it up because I had to work it out twice and would rather nobody else did. Practical question with the units stated, because I have seen how…
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+74 | 78 | 895 | 11mo |
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Why I now write the concentration on the vial in marker
Asking directly, because I could not find a straight answer: Why I now write the concentration on the vial in marker Writing this out with the numbers in it, because "roughly" is how these go wrong. Vial: 15…
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+1 | 5 | 30k | 11d |
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Preservatives: function, testing, and limits
Preservatives: function, testing, and limits — setting out what I have, and where I think it stops being reliable. An honest uncertainty about preservatives rather than a disguised assertion. I do not know…
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+23 | 27 | 3.7k | 16mo |
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Preservatives: function, testing, and limits — one year on
On the subject in the title: Preservatives: function, testing, and limits — one year on Working notes rather than a conclusion. Asking about Preservatives directly, because I have read four threads on it and…
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+28 | 32 | 437 | 8d |
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Second pass at: The storage lookup and where its data comes from
On the subject in the title: Second pass at: The storage lookup and where its data comes from Working notes rather than a conclusion. Two things I would like separated before anyone answers on storage lookup,…
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+38 | 42 | 13k | 19d |
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Why "add 2 mL" is not an instruction
The question in the title: Why "add 2 mL" is not an instruction I will give what I have already checked below so nobody repeats it. Practical question with the units stated, because I have seen how quickly…
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+23 | 27 | 3.5k | 6mo |
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Choosing a concentration on purpose rather than by accident
On the subject in the title: Choosing a concentration on purpose rather than by accident Working notes rather than a conclusion. Working notes on choosing a concentration rather than a conclusion. I would…
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2 | 719 | 1mo |