A drug's expiration date is the date at which the drugs potency decreases to approximately 85% of its original strength. This expiration is determined by aging studies at elevated temperatures, in a specific package that is unopened. These are guidelines set by the United States Pharmacopeia for all manufacturers of drugs in the U.S. It is a requirement for the manufacturer to label its product with an expiration date.
Once a medication has been dispensed in a light and moisture resistant vial by your pharmacy, common practice is to give this drug an expiration of one year. It is not recommended to take a medication past its expiration date; some breakdown of the drug may occur.
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