Since the late 1970's, pharmaceutical companies that sell drugs in the United States have been required by the FDA to stamp an expiration date on the product. The stamped date guarantees the consumer that the drug will be in its full potency until that date. But does the drug cease to be effective on that date or is the expired medication safe to take beyond that date?
Understandably the pharmaceutical companies don't want their products sitting on the shelf indefinitely and a FDA required date stamp allows for quick product turnover on retailer's shelves. But where does that leave the consumer who has a hacking cough at 2am that won't let him sleep and all he has to quiet that cough is a bottle of liquid cough medicine that expired 6 months ago?
Long-term testing has not been done on expired medications, neither prescription or over-the-counter, by their manufacturers. Some government testing has been done on medications which are at least ten years past their stamped expiration date and the results have been favorable, suggesting the medicine is still safe, potent and effective for its recommend use.
Because of potential legal issues, pharmacists and physicians can not legally tell a patient to take expired medications, but in most cases, drugs are safe to take past their stamped expiration date. The exception to this would be certain liquid antibiotics and other drugs comprised of organic ingredients. In other words - if the medicine requires refrigeration it is probably best not to take it past its expiration date.
To ensure over-the-counter and prescription drugs retain their full effectiveness up to and past their alleged prime, store them properly. Store all medicines in a cool, dark, dry place, and the bathroom medicine cabinet does not fit that category. Temperatures in the bathroom fluctuate along with the humidity level, both of which are not an ideal environments for medicines.
A better place for medicine storage is in an airtight plastic container or lockbox on the top shelf of a closet or kitchen cabinet (away from the stove). This will keep the medicine away from humidity, temperature changes and out of reach of children. If taking expired medications is a concern for you, routinely clear out your medicine box and properly dispose of old drugs by taking them to your pharmacist.
The Harvard Medical School Family Health Guide