Determining the precise shelf life of prescription drugs is somewhat difficult. While labels are used and do indicate an expiration date, the actual effectiveness and true shelf life of prescription drugs may indeed be much longer. With the high cost of drugs, some people are choosing to continue using drugs beyond the expiry.
There is a program, the Shelf Life Extension Program, that indicates most drugs, with a few exceptions, can be both safe and effective when used past any manufacturer's expiry dates. It helps to keep the medicines properly stored in their containers, and even put into the refrigerator, to slow any possible deterioration. This program was originated by the FDA when the Department of Defense asked for studies on the shelf life of prescription drugs because they had stockpiles of expensive prescription drugs with expired dates.
Like many other things, the contents of the unopened container is at its best. Once opened, and exposed to humidity, or light, or other natural factors, the items can begin to degrade. Sensitive drugs such as liquid antibiotics, insulin, and nitroglycerin will deteriorate more rapidly then drugs in solid tablet form. Careful attention should be paid to stated shelf life of prescription drugs in these cases, especially if the condition being treated is a life threatening condition.
There have been some studies that show storage under normal household conditions does not affect the effectiveness of drugs even long after the expiration dates. Some reported that even in bad conditions, drugs retained their original properties up to 9 years or more, and that most drugs remained potent for at least five years after expiration dates. No realistic consumer oriented study has been done for the shelf life of prescription drugs.
Most expiration dates run one to five years after the manufacturing date, and these dates are conservative. Actual effectiveness may run as much as almost five more years, according to studies by the FDA. This includes some antibiotics, tranquilizers, and ulcer drugs.
It may be costs that keep expiry dates so conservative. Manufacturers must maintain samples of all lots or batches of drugs that they manufacture. These samples must be stored in proper conditions and stability tests regularly run on the samples to ensure the quality of the drug over time. It costs the manufacturers lots of money to maintain storage and testing facilities for all these batches of drugs. Eventually, it becomes cost prohibitive and it is simply easier and more cost effective for the manufacturer to give the drug a shorter expiry date. The shelf life of prescription drugs may therefore be longer than the expiry date.
If you are trying to save money and you are considering taking a medication beyond the manufacturers expiry date be sure to discuss it with your physician. If you are unsure of how the drug has been stored you may not want to take it. Heat and humidity can degrade drugs and make them ineffective.
The best advice from an FDA spokesperson is to extend any shelf life of prescription drugs by storing them in the refrigerator. No studies have been done on products prone to spoiling, like blood products.