美国国家公共电台 NPR When Old Medicine Goes Bad（在线收听）

DAVID GREENE, HOST:

And now a dilemma that most of us have probably experienced, reaching for a painkiller or other medication only to discover it's expired according to the date on the label. NPR's Patti Neighmond takes a look at what these dates actually mean.

PATTI NEIGHMOND, BYLINE: It turns out they mean a lot. Expiration dates are based on research showing how long the drug's potency lasts. Drug companies expose their medications to different environments, temperatures and humidity to see when a dose starts to degrade. Pharmacist Mike Fossler is with the American College of Clinical Pharmacology.

MIKE FOSSLER: After, about 10 percent of that dose is gone. That would be considered the end of the useful life of that drug. And then that would be your expiration date.

NEIGHMOND: If you take the drug months or even years past the expiration, it might not do you any harm. But it also might not do you any good, which may not be a big deal if you're treating a headache. But if you're fighting an infection with antibiotics, that could be a problem. In addition to keeping medication up to date, it's also important to store it properly.

FOSSLER: Medicines like the kind of environment that people like. We like it a little dry, and we don't like it too hot or too cold.

NEIGHMOND: Which means the place people often keep medications, the bathroom medicine cabinet, isn't a good idea because it's repeatedly doused with humidity.

FOSSLER: With your shower and things like that. So it's better to find a closet somewhere and keep your medicine.

NEIGHMOND: A dry, cool, dark place. Scientist Barbara Kochanowski with the Consumer Healthcare Products Association says this is particularly true for liquid medication.

BARBARA KOCHANOWSKI: That's often where you see refrigeration required or protection from light required. And anytime those conditions change, those medicines can rapidly degrade.

NEIGHMOND: And get contaminated with bacteria or fungus. If you see changes in color or consistency, those are red flags. Don't take it. So before you even buy the medication, check the expiration date and read the storage instructions on the label. That way, you'll get the most out of it.

Patti Neighmond, NPR News.

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