Expired medications are commonplace and inertia notwithstanding, many of us tend to rely on an intuitive sense of their value in continuing to store and use them. Such drugs can be harmful to health in several ways; they can be unpredictable in effectiveness, simply ineffective, or even toxic.
The formal way of classifying a medication as having expired is through it's labeled expiry date. This date is often set based on a combination of the common properties of the dosage form as well as the stability and expiration studies of the product that have been conducted by the manufacturer. Importantly, this expiry date is contingent on specific storage conditions of the product. Although a medication may pass it's labeled expiry date, it may not necessarily be any less effective or dangerous to consume depending on the product itself, the storage conditions and the circumstances leading up to expiry.
When most medications pass their expiry date under appropriate storage conditions, they are generally taken to have become so variable in effectiveness as to have become unsuitable for use. This often comes about as a result of the degradation of the active ingredients of the medication with exposure to physical, chemical or microbiological variables like temperature, pressure, humidity, light, bacteria as well as other components of the product known as excipients.
Creams may "crack" once their expiry date is passed, leading to a separation of the components and hence provide a non-uniform delivery of active ingredients. This can lead to the poor control of conditions like eczema or acne. Tablet medications can mechanically "powder" off, change in consistency with exposure to water vapor or even experience the contained drug itself becoming ineffective on prolonged exposure to air as occurs with glyceryl trinitrate, an emergency medicine that can easily become ineffective in relieving acute symptoms of chest pain. With common injections, should the acidity change to fall outside a fairly narrow range, significant pain and tissue damage can result from use. With most eye drops, an expiry date of one month after opening is accepted to minimize the potential for dangerous bacterial contamination.
With any medication, once a specific threshold of remaining active ingredient is passed, the medication can no longer be relied upon to deliver accurate doses. This loss of reliability is often exacerbated by the fact that the active ingredients can degrade into various combinations of active, inactive or toxic breakdown products. The common aspirin is for instance, known to react with moisture to breakdown into salicylic acid, which is active, and acetic acid, which is inactive and can lead to toxicity in excess.
While the expiry date provides a useful gauge of when to stop using a medication, there are also many other factors that can informally accelerate the expiry of a medication and make it dangerous to use, chief among which is how the medication is stored. It is oftentimes not just the medication that is affected by storage conditions but also the storage container. Under inappropriate storage conditions, certain containers can leech material into liquid medication preparations, or medication particles can stick to the container rather than remain separated. On average, a 10 degree rise in temperature doubles the rate of chemical reactions that occur to a medication product and can accelerate the rate of bacterial contamination several fold. Just like an ice cream can simply melt or a loaf of bread becomes mouldy much quicker if not refrigerated, many medication products can easily expire much faster when not stored appropriately.
With oral liquid and topical medications, potentially dangerous changes associated with expiry can at times be detected by color or consistency changes, component separations, altered smell or taste (oral preparations). Should a suspicion of expiry arise, a medication expert should be consulted regardless of whether or not the labeled expiry date has been passed.
"Expiry" should also be understood to occur once a supply of medications is no longer used appropriately for it's intended purpose. Consultation with a medication expert is always advised to prevent the inappropriate use of existing medication supplies. Inappropriate use can often occur with self-medication and is harmful. An unfinished supply of a previously used antibiotic may be tried to treat a new infection that is actually untreatable by or resistant to that antibiotic. This practice may not only delay recovery but can also encourage the proliferation of "super bugs" that have resistance to many antibiotics. Another incorrect purpose involves sharing medications and this can be especially harmful if another is allergic to the shared medication or a child or pet is medicated with an adult's medication. Children often require dose adjustments to accommodate their size while many human drugs are often unsuitable for pets. Even a simple food like chocolate that we may enjoy can easily be toxic to a pet dog.
Another mechanism whereby medication expiry is dangerous occurs when an unfinished supply is used despite new information that points to increased precautions associated with the medication or that has led to it's recall. An example is obtaining pain relief from a previous supply of a painkiller like Vioxx (rofecoxib) or Celebrex (celecoxib) in spite of an existing heart condition that is now known to relate to an increased risk of fatality under those circumstances of consumption.
Expired medications that are kept instead of discarded not only take up space but can actually discourage the appropriate use of new supplies in the treatment of illness. A medication cabinet, if not tended to regularly, could eventually contain more expired medications than viable ones and this can lead to the accidental consumption of an expired medication in place of a viable one. It is definitely advisable to clear the medication cabinet of expired medicaitons at least annually if not more often.
A further danger however, lies in how expired medications are disposed of. Expired medications and pharmaceutical byproducts can be harmful to the environment especially when they end up in our rivers and drinking water supply. Hormonal compounds like estrogen from birth control pills and patches as well as antibiotics have been linked to being flushed by individuals and institutions into sewage, draining largely unchanged and collecting in rivers and streams, then returning in tiny amounts into drinking water. Traces of antibiotics could worsen bacterial resistance while estrogens and other steroids are known to change the reproductive characteristics of fish. Even trace amounts of chemotherapy medications have emerged in tap water and this could be severely detrimental to the unborn babies of pregnant women who drink such water. The long-term impact on human health of medications in our rivers and drinking water is as yet unknown but no one would want to wait to find out. We can all play our part by inquiring on and using pharmacy or state-run programs for the disposal of expired medications instead of sending them down the sink or the toilet bowl.
A pharmacist is the expert of choice to approach in handling medication expiry and should be consulted if in doubt. As a general rule, it is always best to safeguard your own health and that of those around you by expeditiously and appropriately discarding all expired medications.
