An expiry date is the date after which you should no longer use a product, whether that product is a drug, a grocery store item or anything else. The product can no longer be guaranteed as fresh, stable, safe or, very importantly, 100 per cent potent.
Drug expiry dates are carefully calculated by drug manufacturers because, after all, when you take any medication you need to know the risks and benefits of taking it.
Health Canada is involved in drug expiry dates, and from time to time a drug recall may involve an incorrect expiry date. Manufacturers, in general, do not sanction the use of medication beyond an expiry date because of legal obligations as well as liability concerns. Indeed, when a manufacturer is contacted regarding stability past an expiry date, they generally decline to comment and rely on the expiry date.
Knowing these parameters for drug expiry dates doesn’t really help you when you have a headache and all you can find in the medicine cabinet is a bottle of expired acetaminophen tablets. You can take comfort in a recent U.S. Department of Health and Human Safety article that found no reported toxicities due to ingestion, injection or topical application of currently available drug formulations, with one exception — tetracycline. While drugs certainly diminish in strength over time, it is only tetracycline that deteriorates to harmful substances that can cause potential kidney damage.
Stability data are based on the drug in the original manufacturer’s sealed container. When you receive a prescription medication, your pharmacist will have checked the expiry date on the original bottle and ensured that for the course of your therapy, the medication will not expire. For drugs that you purchase on your own, or non-prescription drugs, you will find an expiry date right on the bottle, jar or box. Tubes of cream and ointment have expiry dates imprinted on the crimp or flat end of the tube.
Once you open a medication bottle, heat and humidity, and even sometimes light, can accelerate drug deterioration. It is for this reason you need to store all your medication in a dry, cool location away from sunlight. If your medication is a liquid, then you need to check it for any discolouration, cloudiness, or precipitation of ingredients. These can indicate damage to the active ingredients. And, of course, if your medication is frozen or left in direct sunlight, it certainly has the potential to be damaged.
Eye drops, once opened, remain suitable for use for usually no more than a month, regardless of the expiry date. Contamination of the dropper and/or the eye drops themselves can occur making them unsuitable for safe use. If you do use eye drops regularly, make a note on the bottle of the date that you opened them, so you know when you should discard them.
Two drugs used in emergency situations have been studied and both seem to retain some potency even past their expiry dates. Epinephrine used to treat anaphylaxis and naloxone used to treat opioid overdoses both can be used beyond their expiry dates, if that’s all that is available. However, an immediate trip to emergency care is certainly needed.
It’s a good idea to check the expiry dates on all the medications you may have in your home. Discard any that have expired and replace any that you will need to use in the future. You don’t need to hold onto that tube of antibiotic cream from the 1990s; it certainly has expired!