If you’ve ever wondered where the expiration date on your aspirin, cough syrup and contact lens solution comes from, the answer is: from stability testing. Things like drugs, foods and vitamins don’t have indefinite shelf lives. Everything degrades over time, and in the case of drugs, it’s important to know when it is no longer safe to use or consume them.
Stability testing (or shelf life testing) assesses how the quality of a drug, and it’s packaging, varies with time under the influence of environmental factors like temperature and humidity. This test process helps scientists determine whether any physical, chemical or microbiological changes have occurred in the product, and if those changes will affect the safety and effectiveness of the drug studied.
Without such testing, the impact on the consumer taking such drugs can range from simple ineffectiveness of the drug because the active ingredient has destabilized, to outright danger because the product’s preservatives were insufficient and microorganisms have proliferated. In almost all parts of the world, it is a regulatory requirement to fully study drug products for stability (among other things) prior to distribution into the commercial market.
The shelf life of a product is commonly estimated using two types of stability testing: real-time stability testing, and accelerated stability testing. In most shelf-life studies, both of these types of stability testing are performed concurrently using a minimum of three lots of product, and taking into account different container quantities, and all varieties of packaging configurations. Believe it or not, the type of bottle that a drug is packaged in, particularly if it is a liquid, can have a big impact on how well the drug performs during stability studies.
Accelerated stability testing (also known as “stress testing”) starts by placing the drug product into a specialized laboratory chamber that controls for temperature and humidity. A typical “heat stress” study would have the drug product placed in one of these chambers with the temperature set at 40° C / 104°F and relative humidity set at 75%. Those are fairly extreme conditions considering that the typical ambient conditions of your home have the temperature at 72° F with just 40% humidity. The drug products studied are kept under these harsh conditions for up to six months, and interval studies (“stability pulls” to use lab jargon) are made to plot the stability or degradation of the product over time.
Running parallel to the accelerated studies, there should also be real-time stability studies performed on the very same lots of drugs, in the very same container volume and type. These studies are much gentler, and are actually designed to mimic typical storage conditions. A common temperature set point for real-time studies is 25° C / 77° C with a relative humidity of 60%. These studies would be run for the same period of time that was expected for the products total shelf life. For example, if it was expected for a particular drug product to have a shelf-life (or expiration period) of two years, then the accelerated study would be run for 6 months and stopped, while the real time study would be run for the entirety of the two years before stopping. After both of these studies are stopped, the drug product would then be tested for all aspects of safety as well as continued potency of the active claimed ingredient.
Green Scientific Labs is an ISO 17025 accredited test laboratory that has the ability to perform multiple aspects of potency and safety testing on a wide array of products. There are several stability chambers available for both real-time and accelerated studies that are all third party performance validated by an ISO 17025 accredited laboratory. Our experienced staff uses only validated test methods on state-of-the-art instrumentation such as HPLC, ICP-MS, LC-MS, GC-MS, and PCT technology to perform precision testing on your products for everything from heavy metals and residual solvents, to pesticides and microbiological contamination.