I recently read an article about DOD's SLEP (shelf life extension program) for medicines. They were discarding millions of dollars in meds when the 'recommended' shelf life was reached from their war stocks. They did studies, and these have been going on for over ten years, which has found MOST medicine is still uesable years after the 'recommended' shelf life date. It is a classified document, since the FDA which authorized the study etc, did not want to upset the phamacutical companies by letting civilians know their antibiotic was actally good three years later. The news was leaked but not the list of hundreds of medicines they have on the list. The article did say however they do not keep nitro capsuls and some other meds that are 'life or death' at the moment beyond the 'recommended' date. With that said, if it doesn't require refrigeration, it may well be potent enough to work. Doses might have to increase, but that's better than throwing it out as useless.
FB
https://slep.dmsbfda.army.mil/ - good luck getting into this site.
http://www.upmc-biosecurity.org/webs..._med_cntr.html
http://www.medicaltuesday.net/VoicesofMedicine.aspx