Question from Chilliwack, British Columbia, Canada:

When my son was first diagnosed we were given a prescription for 10 mL bottles of Regular and NPH insulin and told that unopened, they could be kept in the fridge until their expiration date. These bottle have little caps over the rubber sealed top. When we received further training, we were given a prescription for 3 mL pen cartridges, so as to have less cost/waste (given that our son is on a very low dose of insulin). These cartridges don’t have the little cap over the rubber seal, but are sealed in individual compartments separated by perforations.

When I first separated one vial from the others, I accidentally ripped the second compartment. I didn’t think quickly enough to use that vial, and so it has been sitting in the fridge for a month now. Should I consider this to be “open”, even though I have not punctured the rubber seal with a syringe, and thus discard it? Will it be safe to use when we need to open another vial? Is the cartridge considered “unopened” when the perforated compartment is not broken or when a syringe has not been inserted into it?