Should I throw out expired medications?

DEAR DOCTOR K:

Sometimes the pills in my medicine cabinet reach the expiration date. Do I really need to throw them out? They can be expensive.

DEAR READER:

The two questions to ask about pills that are past their expiration date are: Do they lose their strength, and do they become toxic or harmful?

There is little evidence that outdated medications become toxic or harmful. However, some drugs do lose their potency, or effectiveness, over time. The most notable is nitroglycerin, which should be replaced every six months. The epinephrine in EpiPens also loses its potency past its expiration date. You absolutely do not want to take the risk of needing a nitroglycerin pill to treat sudden heart pain — and having the pill not work. Likewise with EpiPens to stop a severe allergic reaction.

In addition, liquid drugs are less stable than tablets or powders. Liquid drugs include oral suspensions and solutions and injectable products. As a general rule, I would get a fresh refill of liquid drugs when they pass their expiration date.

Most drugs, however, retain their strength past their expiration dates. In one study, for example, researchers tested 96 different drugs stored in their original containers. They found that more than three-quarters of these drugs would remain stable for nearly five years beyond their expiration dates. And a study of two anti-influenza drugs found that these drugs remained fully active after 25 years of storage!

Drug companies generally give their products an expiration date two to three years from the date they’re manufactured. Then, your pharmacist labels your bottle with an expiration date that’s usually one year from the day your prescription is filled. So the expiration date you see on your pill bottle is usually sooner than the expiration date the drug company has assigned your pills.

Expiration dates shouldn’t really matter with a medicine to treat a temporary problem — like taking an antibiotic for strep throat, for example. You should have swallowed the last medicine long before its expiration date.

And expiration dates shouldn’t matter for a medicine that you are supposed to take regularly for a chronic problem, such as to keep your blood pressure normal. If you are taking the medicine as prescribed, it should never have an expiration date that already has passed.

In fact, expiration dates should be an issue only when you have a medicine for a recurring temporary problem. I’m thinking of a strong pain pill for back pain that flares up from time to time, for example, or an antibiotic for a recurrent urinary tract infection.

Remember that the favorable results I mentioned apply to medications that have been stored properly. Always keep your drugs in a cool, dry place in their original containers. And toss out medicines you no longer need. Their presence in your medicine cabinet can be confusing and could cause you accidentally to take the wrong pill.

(This column is an update of one that ran originally in October 2011.)