Tandem gave a webinar today and the presenter explained why they recommend changing the pump cartridge every time you change the infusion set. She said the plastic liner in the cartridge makes the insulin “sticky” and that can lead to clogged tubing and other difficulties in delivery.
I was shocked that they had apparently used a liner that reacts with the insulin and degrades it. This is the first time I have ever heard that explanation. I would not be using a Tandem pump if I had known that the insulin it pumps into my body is degraded by being in the pump cartridge.
EDIT: Found the answer!
My conversations with Tandem reps did not bring enlightenment although they tried to be responsive. But a simple Google search found this in a Tandem submission to the FDA:
Insulin Compatibility and Stability:
In vitro testing was performed to assess extractables and leachables and insulin compatibility with the insulin drugs Humalog and Novolog. To support the compatibility of these insulin analogs the stability of Humalog and Novolog were evaluated for 6 days at 25°C and under stressed, worst-case conditions for up to 3 days at 37°C. The studies observed acceptable results of degradation products, extractables, and leachables, and support the compatibility with these insulin analogs.
The report is here.
That answers my chief question, leachables. Wish I knew more about “acceptable results” but we just have to accept the opinion of the experts. And it would be nice to know what would happen after the 6 day or 3 day test periods, but I am assuming that things went downhill or they would have submitted longer test periods. I am going to use my Tandem carts for less than six days now, about half what I was using them for. And I certainly won’t be using them for any insulin but Humalog or Novolog.