There should be an expiration date on the package--if its expired then I would not use it; pesticides can break down and become less effective or more toxic with time.
Thanks so much, Dr. Coyner!
Well... it dawned on me to check the Frontline Web site, planning to look up the lot numbers because I couldn't find an expiration date on the packages I had in the pet drawer (some with a vet's label from 2006). Here's what I found:
"FRONTLINE Brand Products do not carry an expiration date. We recommend storing FRONTLINE Brand Products at room temperature and keeping them sealed in their original packaging. If stored under these conditions, FRONTINE Brand Products will not expire."
How intriguing, a product which never expires, good to know!
Yes, most of the flea and tick meds don't have expiration dates as they have a very, very long shelf life as they are very stable.
Thanks Dr. Lee. I guess they must be OK... the company would have no financial interest in saying "no expiration date" unless it was really true. (Because if they DID put an expiration date on the meds, people would throw out old ones and buy new ones... as it is, I'm glad I don't have to shell out any more right now, as we're still trying to get a diabetic kitty regulated! so numerous trips to the vet for glucose curves. Now I digress...)
Thanks again, doctors!