Remember that the information presented here is not intended to replace the care of your own doctor. Before making any changes in the management of your own illness, you should consult your physician or other qualified medical professionals.
Question
I have a cat with diabetes, and I am looking to switch him from PZI to Lantus. However, there is some confusion as to whether the vials are good for more than six months or expire 28 days after opening. The pharmacist says they expire within 28 days, but all of the feline diabetes websites state that it is good for six months. My cat will require such a small dose that I would be throwing away most of the bottle each month if it is not stable post 28 days.Answer
The Lantus label states the following:Storage: Unopened Vial/Cartridge system: Unopened LANTUS vials and cartridge systems should be stored in a refrigerator, 36°F - 46°F (2°C - 8°C). LANTUS should not be stored in the freezer and it should not be allowed to freeze. Discard if it has been frozen.
Open (In-Use) Vial/Cartridge system: Opened vials, whether or not refrigerated, must be used within 28 days after the first use. They must be discarded if not used within 28 days. If refrigeration is not possible, the open vial can be kept unrefrigerated for up to 28 days away from direct heat and light, as long as the temperature is not greater than 86°F (30°C).
The molecule becomes more unstable as time goes by, so it's more likely that there will be precipitation of the insulin crystals after a month or so. Closed bottles can be stored until the expiration date that's printed on the carton.
Now, having said all that, it's quite possible to use a product beyond the defined shelf life. The product doesn't automatically disappear like Cinderella's coach turning into a pumpkin. However, in six months, it's very likely that the Lantus (or any insulin, for that matter) would lose an unknown amount of potency, and if the same dose were given every time, there would be a gradual rise in blood glucose. This would probably be countered by an increase in dose (if checking blood glucose levels). Then, whenever a new bottle is used, if the dose is not readjusted downwards, there is a high likelihood of hypoglycemia.
I'd suggest you discuss all this with your cat's veterinarian.
