October 24, 2012
Drugs Maintained Potency Even Decades After
Chicago—What do expiration dates on pharmaceutical labels really mean? Apparently they have little to do with when the drugs actually lose potency, according to a research letter recently published in the Archives of Internal Medicine.
The researchers analyzed eight medications that had expired 28 to 40 years before, all discovered in a retail pharmacy in their original, unopened containers. Analysis found that 12 of the 14 drug compounds (86%) in the medications tested in concentrations of at least 90% of the labeled amounts, the minimum acceptable potency. Three of the compounds were found to be greater than 110% of the labeled content. Two of the compounds—aspirin and amphetamine—were less than 90% of the labeled content, while another compound, phenacetin, measured as greater than 90% in one medication but less than that in another medication containing the drug.
The authors say their findings were interesting but not really surprising. “Expired medications have not necessarily lost potency, since the expiration date is only an assurance that the labeled potency will last at least until that time,” they write. “Clinical situations may arise in which expired drugs might be considered owing to lack of viable alternatives or financial concerns.”
They note that when the FDA’s Shelf-Life Extension Program checked long-term stability of federal drug stockpiles, 88% of 122 drugs stored under ideal conditions had their expiration dates extended more than a year, with an average extension of 66 months and a maximum extension of 278 months.
“The [FDA] permits ‘reasonable variation,’ such that most medications marketed in the United States contain 90% to 110% of the amount of the active ingredient claimed on the label,” the authors point out. “Drug expiration dates typically range from 12 to 60 months after their production. However, FDA regulations do not require determination of how long medications remain potent after that, allowing manufacturers to arbitrarily establish expiration dates without determining actual long-term drug stability.”
|U.S. Pharmacist Social Connect