The Food and Drug Administration has required expiration dates on medications since the late 1970s. Using expired medications can be risky and potentially harmful to the patient’s health. Not only is there the possibility that the medication is less effective, but there is also a chance that there has been growth of bacteria or degradation of the drug that can lead to toxic effects.
One example of a medication becoming toxic after its expiration date is with the tetracycline class, such as doxycycline and minocycline. Ingesting expired tetracyclines has been shown to cause a dangerous syndrome that results in damage to the kidneys (1).
Expiration dates were enacted to ensure that every medication contains at least 90% of the labeled dose and toxic degradants don’t exceed acceptable limits. Once the potency drops below 90%, the manufacturer will consider this to be the drug’s expiration.
Expiration dates are determined by the manufacturer of the product through stability testing. This testing ensures that the drug’s potency, or the amount of drug that the product claims to have per the label, and the integrity of the drug, or its ability to retain the same characteristics over time even after being subjected to changes in things like temperature and pH, remain intact.
It is very important to realize that the expiration date placed on a drug refers to the unopened container. Once the container is opened, this expiration date may no longer apply. Often, the medication box or package insert will inform you if there is a new expiration or “beyond-use” date that should be followed after the original packaging is breached. An example of this is with Atopica (cyclosporine) liquid. Once opened, the contents of the 5 mL bottle should be used within 2 months and the 17 mL bottle should be used within 11 weeks.
Note that proper storage of medications is required for them to remain stable and potent up until the expiration date. Medications should be stored in dry, cool spaces away from light. Clients should be counseled that they should not store medications (for their pet or themselves) in the bathroom or medicine cabinet as the heat and humidity from the shower can have an adverse effect on the drugs.
Within the clinic, heat and humidity should be kept constant. If the manufacturer’s recommendations are exceeded, then the drugs are considered adulterated. Adulterated medications are those that contain decomposed or putrid material; have been produced, prepared, packed, or held under unsanitary conditions and/or not in accordance with good manufacturing practice; contain an unsafe color additive; have strength and/or quality or purity that differs from that recognized by an official compendium; and are mixed or packed with another substance that reduces its quality or strength (2). Expired medications fall under the category of having a strength, quality, or purity differing from the official compendium, and therefore it is illegal to use them.
Many medications also require protection from light even when they are in their original packaging. There are many examples of medications, such as buprenorphine, that come in glass vials, instead of amber vials, but have a notation on the box that they should be protected from light. It is important to review the medications you keep in stock to make sure you are storing them all correctly.
Lastly, any injectable medications that do not have an expiration or use by date following the first puncture listed on them should be expired out after 28 days.
- Litzinger, Mark H.J., and Mersedyes Boatman. “Fanconi Syndrome.” U.S. Pharmacist, Johnson Medical Information LLC, 20 June 2011, www.uspharmacist.com/article/fanconi-syndrome.
- U.S. Food and Drug Administration website: www.fda.gov/medical-devices/regulatory-controls/general-controls-medical-devices/
This month’s column is from Alex Gochenauer, PharmD, FSVHP.