Have you looked in your medicine cabinet lately? Still hanging onto that antibiotic from your head cold two year ago? If you are, you should think twice before taking that medication. You see, most expired drugs lose potency, however, some can become dangerous or even toxic as they age. There are also other problems with taking expired medications as we will see in a minute.

 Most drugs simply lose potency as they age. It is true…the drug does not stop working the day after the expiration date. However, when you take an expired drug, there is no way to know how much of the labeled dose is actually left active. For example, aspirin turns into acetic acid (vinegar) slowly over time, losing its ability to work effectively. Potency can be a problem with antibiotics in particular. It is a problem that not only affects the person taking the antibiotic, but others in the community as well. Using antibiotics that are less than full strength can encourage the production of resistant bacteria. Bacterial resistance in our environment is a huge problem. As bacteria figure out ways to overcome the effects of our antibiotics, we struggle to invent more antibiotics to take their place.

A lack of potency can also become a problem when the drug is used for a serious condition like high blood pressure, high cholesterol or heart arrhythmia. In these cases it is extremely important that the medication have its full potency so the full benefits of the drug can be realized. Some medications (like those for heart arrhythmias and those that thin the blood) have a very small therapeutic index. This means that small variations in their doses can mean life or death.

There are other dangers of taking expired meds. Some medications become toxic as they age. Certain antibiotics can change chemically over time and harm the kidneys when the expired product is taken. Other drugs like eye or ear drops can lose their sterility over time. Introducing a non-sterile solution into the eye or ear can lead to infection.

Finally, consider this. When you first received the prescription for that drug 2 years ago, your pharmacist checked for drug interactions against your current drug profile. You may find that your medication profile has changed since then. If you take that old drug, you open yourself up to possible drug interactions.

Of course it is not always dangerous to take an expired medication. Some medications hold their potency and remain safe for a year or more after their labeled expiration. Some do not. If you are ever unsure about a certain medications safety after its expiration, ask your pharmacist.

Author: Christi Larson, Pharm. D.