On the subject in the title: Filter needles: when they help and what they cost you Working notes rather than a conclusion.
Trying to work out what would count as evidence on filter needles, before collecting any. This is the part I usually skip and it is the part that makes the rest useful.
If two explanations predict the same observation, observing it does not help. So: what observation would separate them?
Sharps disposal: needles and syringes should be disposed in a sharps container (a rigid, puncture-resistant container). Do not put them in regular trash. Many pharmacies accept filled sharps containers.
Picking up post #2: that is the part I would want checked first.
Safety-engineered needles are worth using if you have children or anyone else in the house, and the retraction mechanism occupies dead volume that ordinary syringes do not.
Adding it because I spent an afternoon working it out and nobody should have to twice.
If someone has run filter needles properly I would rather read that than my own reconstruction of it. Posting mine only because the thread has gone quiet.
Coming back to post #4, because the follow-up matters more than the original answer.
Agreed on filter needles, with one qualification that I think matters. The reasoning holds for the case as described. Change the starting assumption and it does not, and the starting assumption is the part nobody states.
Sharps containers are a legal requirement for disposal in several jurisdictions and a sensible precaution everywhere. A rigid sealed container is the minimum.
A guess, clearly labelled as one.
Post #6 answers the question as asked. The question underneath it is different.
Filter needles are for drawing from glass ampoules where particulate is a real risk. For a stoppered vial they add dead volume in exchange for very little.
Not a strong opinion, just a consistent one.
I read post #8 twice before replying, because I had assumed the opposite.
I would put moderate confidence on the mainstream reading of filter needles and no more. That is not scepticism for its own sake; it is where the sourcing actually stops.
Following, with nothing to contribute beyond having asked the same thing elsewhere.
Reading back through the filter needles threads from last year, the same three questions come up every time and only one of them has ever been answered properly. That seems like a documentation gap rather than a knowledge gap.
Post #13 is right about the mechanism and I think understates the practical bit.
What I would want before treating filter needles as settled: the method, the sample, and whether anyone tried to find the opposite result. Two of the three are usually missing.
Post #13 and I disagree about the size of the effect, not about the direction.
U-100 means the barrel is graduated for a solution containing one hundred units of insulin per millilitre. For anything that is not insulin, the units are simply hundredths of a millilitre.
I am aware this is the third time this month I have made this point.
Fixed versus detachable needles: insulin syringes usually have fixed needles (no dead volume loss to the hub). Luer-lock syringes use detachable needles (more dead volume). Fixed needles are preferred for small doses.
Reporting the observation and leaving the explanation open deliberately.
Marking my uncertainty on filter needles explicitly. I am confident about the direction, much less confident about the size, and not confident at all that it generalises past the case in the first post.
Post #15 put the caveat in the right place and I want to underline it.
U-100 means the barrel is graduated for a solution containing one hundred units of insulin per millilitre. For anything that is not insulin, the units are simply hundredths of a millilitre.
That is a fair summary of where the discussion has got to.
Gauge is the outside diameter and higher numbers are thinner. Thinner needles hurt less and draw more slowly, which is the entire trade.
It is worth checking rather than assuming, which costs nothing.
Building on post #21 rather than restating it.
Filter needles would be much easier to settle if anyone reported the denominator. Almost nobody reports the denominator.
Sharps containers are a legal requirement for disposal in several jurisdictions and a sensible precaution everywhere. A rigid sealed container is the minimum.
Somebody will have a better source than mine, and I hope they post it.
The quoted dead-volume figures for common configurations vary between manufacturers and the ordering is stable: fixed needle least, luer with hub more, luer with filter needle most.
Sharps containers are a legal requirement for disposal in several jurisdictions and a sensible precaution everywhere. A rigid sealed container is the minimum.
Adding a source would improve this post and I do not have one to hand.
Picking up post #28: that is the part I would want checked first.
Trying to state the filter needles position in a way that someone who disagrees would recognise as fair, because I do not think the version in this thread passes that test.
Needle gauge: smaller numbers (30G) are finer and less painful. Larger numbers (25G) are courser. For subcutaneous injection, 27-30G is typical. Finer needles take longer to draw up but hurt less.
That is a description of practice, not a recommendation of it.