How long is tessalon good after expiration date?

It's not! Medications are given expiration dates based on how long they have been proven to contain the active ingredient at a certain percentage. Although many medications simply become less effective past the expiration date, there are several medications that may become toxic and dangerous once past the expiration date. Therefore, all medications should be disposed of after their expiration date.

Acually over the counter meds, among many others usually do stay good longer than the expiration date. google the fda military study which will give you good information