The expiration date doesn’t mean, or even suggest, that the drug will stop being effective after that, nor that it will become harmful. “Manufacturers put expiration dates for marketing,rather than scientific reasons ” said Mr. Flaherty, a pharmacist at the FDA until his retirement in 1999.
“It’s not profitable for them to have products on a shelf for 10 years. They want turnover.”
The FDA cautioned there isn’t enough evidence from the program, which is weighted toward drugs used during combat, to conclude most drugs in consumers’ medicine cabinets are potent beyond the expiration date.
Joel Davis, however, a former FDA expiration-date compliance chief, said that with a handful of exceptions — notably nitroglycerin, insulin, and some liquid antibiotics — most drugs are probably as durable as those the agency has tested for the military. “Most drugs degrade very slowly,” he said. “In all likelihood, you can take a product you have at home and keep it for many years.”
Consider aspirin. Bayer AG puts 2-year or 3-year dates on aspirin and says that it should be discarded after that. However, Chris Allen, a vice president at the Bayer unit that makes aspirin, said the dating is “pretty conservative” ; when Bayer has tested 4-year-old aspirin, it remained 100% effective, he said. So why doesn’t Bayer set a 4-year expiration date? Because the company often changes packaging, and it undertakes “continuous improvement programs,” Mr. Allen said. Each change triggers a need for more expiration- date testing, and testing each time for a 4-year life would be impractical.
Bayer has never tested aspirin beyond 4 years, Mr. Allen said. But Jens Carstensen has. Dr. Carstensen, professor emeritus at the University of Wisconsin’s pharmacy school, who wrote what is considered the main text on drug stability, said: “I did a study of different aspirins, and after 5 years, Bayer was still excellent”. Aspirin, if made correctly, is very stable.