In some cases its the binder which turns toxic and not the medicine itself. Many medicines become less effective with age but don’t turn toxic.
The link Kartographer provider earlier is a good reference and provided by an MD - http://www.survivalblog.com/2010/07/a_doctors_thoughts_on_antibiot.html
I am familiar with that link.
Even at this stage of the global economy, collapse or not, it is all getting a bit problematic. Shortages of some medications, fewer generics, most production overseas, and I read recently that even common medical supplies, like tubing, are mostly being manufactured abroad.
My husband tries to stay 2-3 years ahead on his personal meds. Otherwise, we have med staff/clinician friends who are stockpiling some injectable antibiotics and other items. So far, they say they have been able to work around the shortages and, of course, they are knowledgeable about substitutions. IMO, they know what is most stable and, as important, which antibiotics, et al, are best for what. From what I read and have learned otherwise, it is important to know which antibiotic to use for which sort of infection. Then, there is knowledge if dosage and side effects/interactions.
That is a lot of knowledge that is not that easy for the layperson to assimilate.