Stability testing is the statistical analysis of how long a pharmaceutical product can be stored without any change in its original chemical composition.
Pharmaceutical products when stored for long durations tend to undergo changes and release byproducts. Stability testing provides evidence on how certain pharmaceutical drugs can be stored at room temperature and in controlled conditions.
Real-Time Stability Testing: This form of stability testing is conducted on drugs for the same duration as the recommended shelf life. In this, regular periodic tests are conducted and conclusive analysis is done for its composition, efficiency, and reaction to various conditions. The trend analysis from this periodic testing is compared with different batches and a linear conclusion is approached.
Retained Sample Stability Studies: This testing procedure is practised for every marketed product that requires stability studies. In this, the stability of the drug is periodically inspected and is allowed a degradation percentage of 2-5. For example, if a pharmaceutical drug has a shelf life of 5 years, the drug is tested in its 3rd, 6th, 12th, 24th, 36th, 48th and 60th month and the changes in its physical, chemical, and microbial composition are noted and compared with the regulated permissible levels.
Cyclic Temperature Stress Testing: This testing procedure is not compulsory and drugs undergo this test on a case to case basis. In this, the minimum and maximum temperature conditions are mimicked in a controlled environment and the drugs are exposed to these conditions for 24 hours and the changes if any are noted.
Normally the drug undergoes 20 cycles of cyclic temperature stress testing before any conclusive analysis on its stability is made.
Accelerated Stability Testing: This is a form of shelf-life testing and is used to gain insights on the predicted shelf life of the drug. In this, the drug is exposed to more than ambient temperatures and the changes are noted. Earlier the drug used to be exposed to extreme conditions and the amount of heat required to cause chemical composition failure was noted. This information was used to extrapolate the shelf life and relative stability of the pharmaceutical product.
For statistical linearity, the drug is exposed to 4 different temperature conditions and the exposure to accelerated conditions after refrigeration is also noted. Now the protocols are simplified and based on target markets and storage conditions, single accelerated condition storage usually at 40 degree celsius and 75% Humidity is used as per ICH.