I use lactated ringers to deliver fluids subcutaneously on my cat with kidney disease. I noticed today that one of the bags' expiration date has already passed.
Is it safe to use? What are the risks/dangers?
If the lactated ringers have been sealed and kept in controlled conditions (stable temperature, humidity, etc), there is a high probability that they are safe to use. If there is any question about the history of product (it sat in someone's car for a few hours), there is no data on the likely performance and it is probably better to discard the solution.
In the United States, the Food and Drug Administration has administered the Shelf Life Extension Program (SLEP) for the Department of Defense for over 20 years. The goal of SLEP is to reduce government spending by testing medications (and other materiel) that have passed their manufacturer's expiration date to determine if the materiel is still useful (so the DoD does not have to dispose of it and repurchase replacement materiel). In 2006, a paper summarized the data that had been collected so far.
Pharmaceutical drug products sealed in original container closures are stored under controlled conditions by the military services.
When the expiration date approaches, a sample (subset) of the lot is sent for testing.
For injectable solutions, the attributes [assessed] were potency, impurities, pH, preservatives, and physical appearance (color, particulates).
During the 20 years reported in this study, 59 lots of lactated ringers were tested. 95% of these lots (56) had acceptable attributes at the time of this study. The expiration date of these lots had been extended a minimum of 23 months and maximum of 125 months. The lots that failed had improper levels of calcium and sodium (the report doesn't say how far off and in which direction the levels were incorrect).
Lyon, R. C., Taylor, J. S., Porter, D. A., Prasanna, H. R. and Hussain, A. S. (2006), Stability profiles of drug products extended beyond labeled expiration dates. J. Pharm. Sci., 95: 1549–1560. doi: 10.1002/jps.20636
I have given many cats many doses of subcutaneous fluids and as long as the bags are stored at an even, average room temperature and kept out of the light, the fluid will be fine.
However, if you detect even a slight clouding or milkiness in the bag, ditch it right away.
As to expired mediation in general. Most medicat6ions will remain effective far beyond the marked date. In fact, the military has done research and they keep large supplies of some types of expired medications because they know they will be safe and effective.
When Eli Lilly discontinued Humulin Lente insulin in 2005, we stocked up, kept it in the refrigerator, and used insulin which was over five years past the "expiration" date. I think we accumulated something like twenty vials of that insulin preparation before we could find no more on the market.
Most, if not all, medications don't turn into poison over time, if they change at all, they simply become less effective or totally ineffective.
We were confident with the expired insulin because we always do a blood glucose measurement on a diabetic cat before giving insulin and we do other spot checks at various times on various days. If the insulin was declining in effectiveness we would have known right away by the change in the numbers.
But, back to IV fluids - store them carefully and throw out any that are even a bit clouding and you and your cat should be just fine.