Solubility limits and what a cloudy solution is telling you — setting out what I have, and where I think it stops being reliable.
The question about solubility limits that I actually want answered is the second one below. The first is context and I have kept it short.
Both are stated with units, and I have said what I already checked so that nobody repeats it.
On the opening post — agreed on the reasoning, with one qualification.
If you are new and reading this thread for the answer to solubility limits: the answer is conditional, the conditions are in the third reply, and the rest of the thread is worth skipping.
Isotonicity: an isotonic solution has the same osmotic pressure as blood. Non-isotonic solutions can cause discomfort on injection. Injectable peptide solutions are formulated to be isotonic.
That distinction has done more work for me than anything else in this category.
Excipients and their purposes: mannitol, sucrose, or other sugars in lyophilised formulations protect the peptide during drying and storage. They are not impurities; they are functional components.
The disagreement above is smaller than it looks once the terms are fixed.
Post #7 is right about the mechanism and I think understates the practical bit.
The bit of solubility limits that nobody enjoys is that the answer changes depending on what you are trying to decide with it. Say what the decision is and the thread will converge.
Freeze-thaw cycling is harsher on a solution than sustained cold, because the ice-water interface is where damage occurs. A single freeze is a different event from five.
Picking up post #9: that is the part I would want checked first.
Solubility limits is worth one more sentence than it usually gets, and the sentence is the one about how the number was arrived at.
Coming back to post #10, because the follow-up matters more than the original answer.
Fill volume and headspace: the amount of solution in a vial and the air above it affect how much the solution is exposed to oxygen during storage. Less headspace means less oxygen exposure.
I would not lead a decision with this, but I would not ignore it either.
Good question, well framed, and I would like to see it answered properly.
Where I would push back on the solubility limits consensus is the confidence, not the direction. The direction looks right. The confidence is borrowed.
| Topic | Participants | Replies | Views | Activity |
|---|---|---|---|---|
|
Buffers, pH and why a formulation is a formulation
Buffers, pH and why a formulation is a formulation Writing it up because I had to work it out twice and would rather nobody else did. A formulation question rather than a pharmacological one, though the two…
|
+11 | 15 | 51k | 21mo |
|
Coming back to: Adsorption to container surfaces and to plastics
Adsorption to container surfaces and to plastics — setting out what I have, and where I think it stops being reliable. Adsorption — I have the observation and I do not trust my interpretation of it, so I am…
|
2 | 459 | 17mo | |
|
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…
|
+23 | 27 | 3.7k | 16mo |
|
Second pass at: Buffers, pH and why a formulation is a formulation
Second pass at: Buffers, pH and why a formulation is a formulation Writing it up because I had to work it out twice and would rather nobody else did. Posting a small dataset on Buffers. It is mine, it is…
|
+24 | 28 | 1.5k | 21mo |
|
Lyophilisation and why the cake looks the way it does
Posting this under the heading it deserves: Lyophilisation and why the cake looks the way it does Everything below is what sits behind that. I was wrong about lyophilisation in a thread last spring and I…
|
+33 | 37 | 60k | 6mo |
| Topic | Participants | Replies | Views | Activity |
|---|---|---|---|---|
|
Aggregates and why a purity assay may miss them entirely
Aggregates and why a purity assay may miss them entirely Writing it up because I had to work it out twice and would rather nobody else did. I would like to disagree carefully with the settled view on…
|
+61 | 69 | 2.9k | 6mo |
|
Second pass at: A reconstituted vial's beyond-use date and the reasoning behind common figures
Second pass at: A reconstituted vial's beyond-use date and the reasoning behind common figures Writing it up because I had to work it out twice and would rather nobody else did. Something changed and I would…
|
+4 | 8 | 20k | 8mo |
|
Excipient function in a licensed injectable — the long version
Posting this under the heading it deserves: Excipient function in a licensed injectable — the long version Everything below is what sits behind that. A narrow question about Excipient function, deliberately…
|
2 | 100 | 15mo | |
|
Priming a pen and whether the primed volume is wasted
Priming a pen and whether the primed volume is wasted Writing it up because I had to work it out twice and would rather nobody else did. I have spent a fortnight trying to pin priming a pen down and I want to…
|
+19 | 23 | 1.3k | 2d |
|
Transporting a vial for a weekend away — a second dataset
Transporting a vial for a weekend away — a second dataset Writing it up because I had to work it out twice and would rather nobody else did. Posting a small dataset on Transporting a vial. It is mine, it is…
|
+74 | 84 | 5.1k | 1mo |