Drug discard date creates discord

The question is common, and it seems so simple. Do we need to worry about medicines going bad if they are used beyond their expiration date?

The answer is a bit more complicated than you might think. We recently received the following question from a reader of this column: “When I picked up a prescription from the pharmacy, the pharmacy label had a ‘use before’ date of 09/04/10. The manufacturer’s label, under the pharmacy label, had an ‘expiration’ date of Dec 2012. Why is this?”

We pointed out that the one-year “use by” date is legally required in many states. It is also convenient, since computers easily can generate a date one year from the dispensing day when printing the label. This date rarely coincides with the manufacturer’s actual expiration date.

Our answer generated controversy, especially among pharmacists. Several were offended by the suggestion that convenience would play any role. A few pointed out that the one-year discard date is mandated by state law.

One gentleman objected to any idea of paying attention to the manufacturer’s expiration date: “I have been a pharmacist in New Jersey for 50 years, and I think your explanation is off-base. The manufacturer’s expiration date assumes that the drug remains sealed in the original bottle under carefully controlled conditions.

“Once the patient opens the bottle and stores it in a bathroom or kitchen, those conditions don’t apply. The heat and humidity will cause rapid deterioration. People may assume that it is all right to use a drug up to the manufacturer’s expiration date, and that would be a mistake!”

Drug companies do test their drugs for stability under controlled conditions. Most drugs have an established shelf life of one to five years, but research shows that they often last much longer.

Extreme conditions can lead to problems, though this is not always due to improper storage by the patient. Mail-order prescriptions are frequently exposed to extreme temperatures even before the patient receives them. When pills sit in a mailbox for hours, they may bake or freeze, depending on the time of year.

Many people worry that medication past its expiration date will morph into something dangerous that could be harmful. Fortunately, a new review from the Medical Letter on Drugs and Therapeutics (Dec. 14/28, 2009) lays that fear to rest. There are no reports of harm from taking a medicine that has exceeded its expiration date. In many cases, drugs retain their potency for up to five years after the manufacturer’s expiration date.

One important exception is injectable epinephrine found in EpiPen. This medicine is used to reverse a life-threatening allergic reaction. Patients are taught how to give themselves injections in an emergency. Once it is past its expiration date, it may not be potent enough to do its lifesaving job. Consequently, EpiPens should be replaced regularly.

Liquid medicine should never be allowed to freeze, and medicine should be stored away from heat and humidity. That means not in bathroom medicine cabinets.

If you want to know the manufacturer’s expiration date for your medicine, ask the pharmacist to put it on the label when you hand in your prescription.