There is a lot of confusion surrounding expiration dates on over-the-counter and prescription drugs. Some people use the stamped date as a loose guideline, others adhere to it strictly, and a few keep their bathroom cabinets stocked with outdated pills indefinitely. One internist, Sharon Bergquist, assistant professor of medicine at Emory University in Atlanta, explains when to get rid of that eye ointment, and why an out-of-date aspirin might be just fine to take.

It's the Law
Since 1979, the Food and Drug Administration has required manufacturers to put expiration dates on prescription and over-the-counter drugs. Most patients don't know what that date actually means. "It is the final date up to which the manufacturer will guarantee that medicine has full potency," says Dr. Bergquist. "But that doesn't mean that is the day that medication will become ineffective or unsafe."

The expiration date is generally anywhere from 12 to 60 months from the time the product was manufactured, says Dr. Bergquist. She notes the date is conservative and in most cases, the drugs in question haven't been tested for efficacy or toxicity past that date. Once a pharmacist dispenses a drug to a consumer, he will often put a "beyond use" or "discard after" label on the bottle, which is generally one year from the time he opened the original container. "This is required by 17 states," says Dr. Bergquist. "But there is very little science behind it. It very well could be that a medication is good for 10 more years."

A Military Study
At the request of the Department of Defense, the FDA conducted a major study of the shelf-life of common medications.

The study, published in the Journal of Pharmaceutical Sciences in July 2006, looked at the Defense Department's large stockpile of drugs from 1986 to 2006 and tried to determine if all of the drugs needed to be replaced. The FDA analyzed 122 drugs in 3,005 lots, and studied their stability. "It turned out that 88 percent of the lots could be extended beyond their expiration date for an average of 66 months—or 5½ years," says Dr. Bergquist.

Of course, she adds, the military stockpile is generally kept in a climate-controlled, regulated area, "not in a humid cabinet in a bathroom."

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