Antibiotics may be potent years beyond the expiration date. I worked in the drug industry and a vp of quality control was in the office next to me. He told me one day that expiration dates on drug bottles had nothing to do with when the medicine was no longer potent. All the FDA wanted to know was the medicine was effective up to that date. What drug companies wanted to do was push the product through the system and a long effective date was contrary to that desire. (Tetracycline may be one exception and an antibiotic that should not be taken after the expiration date.) For what it's worth here's one link to a Wall St Journal story:

http://www.endtimesreport.com/Prescription_longevity.html

Tim W.