Viewpoint: Should an RX label require a use-by date or an expiration date?

As pharmacists, we know that the use of a medication before its expiration date ensures maximum potency if it was stored under proper conditions. Once a medication has been dispensed, the original manufacturer's expiration date cannot always be relied upon and 22 states and the District of Columbia (see table) require the pharmacist to place on the Rx label a "use-by date" or an "expiration date." The "use-by date" is one year from the date of dispensing or the expiration date on the manufacturer's container, whichever is earlier. This "use-by date" required by states is similar to the requirements of the 2007 USP/NF, which indicates that in the absence of stability data for a drug product in a repackaged container, the beyond-use dating period is one year from the date of dispensing or the time remaining of the expiration date, whichever is shorter.