Georgia executed a murderer on Tuesday with drugs that may have been past their expiration date. The state purchased its supply of sodium thiopental—designed to anesthetize a patient during the lethal-injection procedure—from an obscure, and unlicensed, British company. As if that weren’t sufficiently dodgy, the drug, which has a shelf life of just one year when made in the United States, was manufactured in 2006. Are drugs effective past their expiration dates?

Usually, yes. At the behest of the Pentagon, the Food and Drug Administration launched the Shelf Life Extension Program in 1985 to determine whether the military’s massive stockpile of expired drugs had become ineffective. The study, first made public by the Wall Street Journal in 2000, showed that 90 percent of drugs maintained stability—that is, their chemical constituents did not degrade or change substantially—well past their expiration dates. Some drugs were good for a decade after expiring.

The Journal’s report, in which one expert claimed that conservative dates were an industry trick to increase turnover, has spurred significant Internet skepticism over expiration dates. But before you go tossing back vintage Tylenol, consider a couple of caveats. There was surprising variability in the FDA study. Sometimes different batches of the same drug lost efficacy at very different times for unknown reasons. In addition, the Pentagon stores its multimillion-dollar stockpile of medications under controlled temperature, humidity, and light conditions. Your medicine cabinet doesn’t offer an ideal storage environment. And some classes of drugs, like biologics and insulin, are especially likely to spoil. Accordingly, the FDA continues to recommend that you throw away your expired medications.

Unlike food expiration dates, drug expiration dates are regulated by the government. The FDA requires pharmaceutical makers to declare the shelf life of their products after a stability-testing process. Drug makers typically store three batches of the product at 77 degrees Fahrenheit and 60 percent relative humidity, and three other batches at 104 degrees and 75 percent humidity to simulate shipping conditions. In most cases, drugs that survive the process get initial expiration dates between 12 and 24 months from the date of manufacture, depending on how much chemical degradation occurred during testing. Put simply, the expiration date means that the manufacturer has proven that the product will still work at that time. It absolutely does not mean that it will necessarily stop working a day, a month, a year, or five years after that date.

Once the product hits the market, drug makers are permitted to conduct additional testing to prove longer-term storage stability. But this is entirely optional, and there’s little incentive for manufacturers to extend the date. A few have taken advantage of this opportunity, with the longest expiration date on the market currently at 60 months. But many others just stick with the initial label.

Manufacturers claim that there’s no evidence we could save money by conducting long-term stability tests on drugs, but that’s not entirely true. The Pentagon spent $3.9 million on its shelf-life tests and saved $263.4 million in drug costs over a five-year period.

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Explainer thanks Shelly Burgess and Christopher Kelly of the FDA.

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