There is a recall on Iverhart Heartworm Preventative. I have attached a link so if you have any you can check the lot number here:

http://www.aahanet.org/blog/NewStat/post/2013/04/17/768595/Virbac-recalls-six-lots-of-Iverhart-Plus-Flavored-Chewables-due-to-efficacy-concerns.aspx