Have you ever needed a medicine but only had expired pills? In this situation, some will throw out the old pills while others will take the medicine regardless. So the questions arise: How accurate is the expiration of drug? Is it unsafe to take a medication that is expired?
Expiration dates tell us until when a company can guarantee the effectiveness of drugs. Expiration dates have huge variations with some as short as 18 months. Some require refrigeration and some require specialized containers with desiccants, or a substance that has an affinity for water, to keep the product try and enhance stability. Expiration dates are important for the safety of the drug users, so it is, therefore, part of regulation. It is important to keep in mind that expiration dates are based on testing in previously unopened bottles under normal conditions. If a drug is moved to another container or is placed under extreme conditions, its stability is compromised and the expiration date is no longer reliable.
The U.S. Food and Drug Administration has established a number of required quality tests that any drug needs to pass. Drug expiration is dependent on stability tests. Once it is a known that a drug works effectively and consistently, it needs to be established how long this will continue. How long will it take for a drug to deteriorate? The first thing you need to know is how expiration dates are calculated. It is impractical to wait a few years to see the effect time has on a medication, so an alternative method is utilized. This alternative method is known as a stress test, or a degradation test. The specifics of a stress test varies for each individual case, but in general, stress tests includes checking the effect of temperature, oxidation, photolysis, and sometimes humidity. It also includes testing the susceptibility of a drug to hydrolysis across a wide range of pH’s. Stress testing is useful as it can not only determine an approximate time for a drug to degrade, but it also can help establish the degradation pathway. Therefore, it is known what exactly is happening to the drug over time under certain conditions. For liquid and injectable drugs, additional testing is required to determine bacterial purity and chemical stability.
So now we come to the question of the safety of expired drugs. Fortunately, there is currently no data that shows harmful effects of expired drugs besides a discontinued drug (tetracyline) from the 1920’s. There are case occurrences, but these are quite rare. Also, stability testing requires that drugs should identify if the expired product will pose any safety risks. The effectiveness just decreases with time. However, the effectiveness is still quite high for a while after expiration typically. The Shelf Life Extension Program (SLEP) has studied 122 different drugs and 88% were still effective at least 1 year after expiration. The average was a 66 month expiration extension. Therefore, if properly stored, it is safe to use drugs past expiration and the drug might still be very effective. So the next time you only have expired medication left, you know the information you need to make a decision to take it or not.