Q. Is dewormer still good after its expiration date?

—Lynn, Chicago, Ill.

A. Like all medications, dewormers have a limited shelf life, which is determined through drug stability testing. The expiration date on the label is the latest date for which the manufacturer can guarantee full product potency.

In addition to the expiration date, equal consideration should be given to proper product storage. If the dewormer was stored outside the recommended temperature range listed on the label (i.e., in the tack room or horse trailer where it could have gotten too hot or too cold) its drug stability will be negatively impacted, as well