I think this has been mentioned before, but it seems to bear repeating: Drug expiration dates are arbitrarily selected by the manufacturers to maximize movement of their product off the shelves. They bear no resemblance to what is actually happening chemically, which, with the exception of insulins, nitroglycerin, and possibly, tetracycline, and some liquid antibiotics, is next to nothing:

http://articles.mercola.com/sites/articles/archive/2000/04/02/drug-expiration-part-one.aspx.

With the possible exception of outdated tetrcycline (this is controverted), NOTHING else turns into a poison past it's due date. There may be a trivial loss of potency, but that is all. If the aspirin or ibufprofen turns an 7/10 headache into a 1/10 headache, rather than a 0/10 headache, well I think we can all cope.

I remember one of my well-intentioned kids coming home from school with an assignment from a well-meaning teacher: check the expiration dates on all the stuff in medicine cabinet, and pitch anything past it's expiration date. I'm sure the drug companies and their stock-holders were happy with the result; perhaps they have had a role in writing the erroneous curriculum used by the health teachers to perpetuate this myth.