Stability testing is a vital part of product development and is conducted throughout a product’s life cycle (Figure 1).Stability is part of a biotherapeutic’s quality target product profile, and results help analysts understand how critical quality attributes (CQAs) of both drug substances and products are influenced under specific conditions of temperature, relative humidity (RH), light, storage, p H, and other factors.
Prototype testing is performed during early stages to characterize a product or formulation.
Testing in Stages All stages of a biologic’s life cycle includes stability testing.
Experts have divided these tests into six stages, covering development from early stages to late-stage follow-up testing (1, 2): The information that is obtained during testing depends on the stage of development.
Failure on the basis of potency, p H, water content, dissolution, physical appearance, or presence of impurities occurred in 479 lots (~18%), but none failed within 1 year.
Potassium iodide, which has been extensively stockpiled for use in a radiation emergency, has shown no significant degradation over many years.4HEAT, HUMIDITY, AND LONG-TERM STORAGE — Storage in high heat and/or humidity can accelerate the degradation of some drug formulations, but in one study, captopril tablets, theophylline tablets (, and others), stored at 40°C and 75% relative humidity, remained stable for 1.5-9 years beyond their expiration dates.5 In another study, theophylline retained 90% of its potency 30 years past its expiration date.6 A study of eight products that had been stored in their unopened original containers for 28-40 years past expiration found that 12 of 14 active ingredients had retained ≥90% of their original potency; aspirin retained 50 years past expiration) were all found to contain significant amounts of the drug.8 Drugs in solution that have become cloudy or discolored or show signs of precipitation, particularly injectables, should not be used.