hi @MarkCK I suppose it seems that the literature included with the medicine is saying one thing and your experience is saying something else… This is a case where the manufacturer is right and you are right at the same time for different reasons. I support engineering for (research and manufacture) sterile biological pharmaceuticals so I’m speaking from 29 years of manufacturing and quality experience.
All pharmaceutical literature relating to storage requirements are based on stability data from controlled environments and represent (typically) either 1 out of a million or 1 out of 100 million certainty. Put another way - NOTHING HAPPENS if you have 100F insulin for 4 days… usually. The literature says if you obey the discard rules then you will NEVER EVER have insulin efficacy degradation. When the degradation can include serious injury or death, then most pharma go for the certainty of 1 out of 100 million.
quick example: Milk. Milk does not magically go bad on it’s expiration date, every time period after the expiration date, your chances of sour milk go up by about 2^n (two to the n power where n is the time scale, standard, or duration) until at some point, there is a 100% chance of bad milk.
So are we all doing it wrong? yes and no. we are playing, quite successfully, in a margin outside the pharma acceptable risk of 1 out of 1 million certainty. if you have ridden your bike 1 million times, you are very likely to have spoiled insulin 1 of those times. if you ride 7 days a week, that’s about once in 2 thousand years of bike riding.
In my opinion, please don’t get hung up on the binary good/bad do/don’t from the literature set. Your experience is representative of what we all see. The risk is infinitesimally small… unless you plan on living 3000 years.
as far as medicine in contact with plastic, Lilly and Novartis could give a darn about what kind of reservoir and they are not required to include stability data for someone else’s reservoir or pump. That falls on the plastic reservoir manufacturer. Thingks like reactivity, carbon dioxide infiltration, oxygen infiltration, “leachable” chemicals from the plastic all fall on the reservoir manufacturer (typically a subcontractor to the pump manufacturer) and NOT the insulin manufacturer.
In the USA, there are extremely strict regulations on responsibility and testing, and this is a very large part of why change comes very slow, and are expensive. However, it is necessary for limiting errors and risk to patients. The EU and Asia can develop their own regulations but most simply copy the US standards.
most folks using insulin have never read the literature. you are quite detail oriented and would make a good engineer.
I posted that PDF up there because it was one of the few pieces of officious information I found on the time you are allowed to keep insulin in the reservoir. After my last new pump educator told me I shouldn’t preload cartridges, I wanted to know why. (Engineer.) And you know what? I still don’t know why. Your comment is as close as I’ve seen to an explanation of why.