Howdy - long time lurker, first time posting,
A lot of good info in this thread.
A couple things that should be avoided; aspirin (ASA) will degrade into toxic components after expiration date. I don't recommend ASA for anything really anymore. Tylenol (APAP) or Motrin (IB) can do the same as ASA but with less side effects and even less allergies than to ASA. About the only thing i would use ASA for is baby aspirin for chest pain, and even that is controversial these days. Follow your protocols
Nitroglycerin (NTG) will lose if efficacy after its exp date and if not kept in opaque containers. If you need NTG, you probably already know this. NTG should only be administered if you know what you're doing and have the appropriate medical training and gear in case the patient's BP bottoms out.
I read a study a few years ago (that I can't seem to find anymore) about the efficacy and strength of expired Epi-pens. The study offered new, in date, epi-pens on a one-for-one exchange to anyone no matter what condition. They received quite a large sample as I recall. The pens had been kept in various conditions; some were kept in refrigerators while some rattled around in back packs or glove boxes for years. Some of the pens had just expired and some had been expired for years. When the epinephrine was withdrawn and tested; all samples were still in compliance with FDA potency regulations. A similar study, published around the same time, did the same test with some medicines that were taken from various health clinics around Africa. This test also found the same results as the epi-pen study.
When I was in the Army, our Brigade Surgeon would routinely extend expiration dates from six to 12 months. My physician medical control would do the same thing at my last job.
Just some more info to ponder. If it was me, I would rather treat a person with expired meds and potentially save their life than not treat. I'll deal with legal repercussions later.
Get some medical training and certifications and stay in your lane when it come to treating people. Do not treat beyond your scope of practice and you should be good to go.
Y'all take care