Usually when medication expires, it just loses its potency.  You could always call the poison control hotline if you are uncomfortable.

I think as with any med's if you hav'nt taken them for a while it is best to look at the ex date, but I agree with lovin life, I think it just loses potency.                          
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It won't hurt you.  It just may not work, that is all.  You won't even get ill.