I used to work in QA for a major drug company where we'd store the drugs for years at different temperatures and humidity, and every 3/6/12/18/24/48/60 months we'd test them in spectrometers, as well as testing for clumping in powders, colour changes, etc. One of our jobs was to make sure they didn't turn into anything nasty, but it was mainly making sure they stayed stable.

For all day-to-day drugs it's really a precaution rather than anything else. Usually they just become a little less effective by becoming less concentrated, but most of the ones I worked with even the 50/80(?) ones were still fine years later (stored at 50 degrees celsius, 80% humidity (I think? Was 20 years ago)). We had a special warm room where all the samples were kept.

Heh. Funny sorry:

One time I was on a drug that had to be shipped to me from an out of town pharmacy in a refrigerated vehicle. The delivery guy demanded that my apartment leasing office refrigerate it, which led to them almost losing it.

Next time I had it shipped to a local pharmacy instead for pickup. That pharmacy didn’t refrigerate it at all and insisted that was kosher. (They also almost lost it.)

I called the original pharmacy and they assured me it doesn’t actually need to be refrigerated, as long as it doesn’t reach its melting pint of like 100 F.

The package said it needed to be refrigerated.

Sometimes the official recommendations they file with the FDA and what they know from their internal testing vary.

If you call the company, they can basically answer any question you ask, even for un-approved indications.

But for them to bring it up without you asking is a big Nono.