Medications past best-before date may lose potency, but how soon?

Expired medication is seen in Toronto on Thursday, April 9, 2015.
Image Credit: THE CANADIAN PRESS/Graeme Roy

TORONTO - The recall earlier this week of a batch of Alesse birth control pills sold past their expiry date has raised questions about whether it's safe to take over-the-counter and prescription medications beyond their best-before marker — and just how long past?

"I think it would alarm a lot of Canadians if they knew that there isn't a lot of study on this," said Phil Emberley, director of pharmacy innovation at the Canadian Pharmacists Association.

Drug manufacturers must provide evidence on the potency and safety of products related to short-term exposure to light, heat and humidity in order to get market approval, but they aren't required to furnish federal regulators with data on long-term shelf-life, Emberley said from Ottawa.

Typically, manufacturers give their best estimate of how long they believe a medication will retain 100 per cent of its potency, he said.

"But there is no firm evidence that that is in fact true," said Emberley. "Two years later, it still could be potent. It's just that they've never done the studies."

Emberley said it's in manufacturers' best interest to be somewhat conservative in choosing best-before dates "because they could face legal liability if it's shown that these products expire sooner than later."

"And also it allows them to sell more product as product expires and people need to replenish what they have."

The research that has been done on the long-term viability of medications includes a Food and Drug Administration study conducted at the behest of the U.S. military, which wanted to determine if its large and costly stockpile of OTC and prescription medications were still usable. After assessing more than 100 drugs, the FDA found that more than 90 per cent were still effective well after their expiration dates, some as long as 15 years later.

Still, Emberley said best-before dates shouldn't be taken lightly.

In the case of Alesse 21, the pills were sold in western Canada in March and April, but carried an expiry date of last September. It's not known if women who took these oral contraceptives received a fully potent dose or whether they are at risk for unwanted pregnancy.

Other prescription drugs could also lack effectiveness if the expiration date has gone by, and some could be potentially harmful. For example, taking out-of-date nitroglycerin, used to treat angina, could have severe repercussions if potency has waned, Emberley said.

As well, he said, manufacturers' expiry dates are based on unopened products.

"So if you have a bottle that, say, expires in five years, as soon as it's opened technically it expires in less than five years," he said. "A lot of people keep their medications in their bathrooms where they're exposed to heat and humidity, and there is evidence to suggest that it speeds up the degradation process."

Suggesting it's better to be safe than sorry, Emberley advises consumers to cull any out-of-date drugs from their medicine cabinets and take them to a pharmacy to be destroyed.

Dr. David Juurlink, head of clinical pharmacology and toxicology at Sunnybrook Health Sciences Centre in Toronto, said concerns about diminished potency depends on the drug and how much time has elapsed since the best-before date.

"For most drugs, the passage of a short amount of time after the expiry date is really of little clinical consequence," he said. "In general, something that's six to 12 months past the expiry date, with rare exceptions, is not going to be a problem at all. They're not going to be dangerous."

A 2012 study of a small number of drugs — some of them bottled or packaged 40 years earlier — found that active ingredients did degrade over time, but some more than others. For instance, researchers found ASA pills dropped in strength from 200 milligrams to two milligrams, while codeine barely lost any of its chemical constituents.

"It's not like milk, and it's not as though something magical happened on the expiry date and the drug loses all of its potency," Juurlink said. "With most, but not all, it's probably safe to take drugs that have expired recently. But the more time that has elapsed from the expiry date, the less advisable it becomes."

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