Medication expiry dates are established through regulated stability testing conducted under standardized environmental conditions of temperature, humidity, and light exposure. These studies evaluate chemical integrity, potency retention, microbiological safety, and physical characteristics of pharmaceutical formulations over time. The labeled expiry date, therefore, represents the period during which manufacturers guarantee full therapeutic efficacy and safety when the product is stored as recommended. Regulatory authorities such as the U.S. Food and Drug Administration and India’s Central Drugs Standard Control Organization mandate stability data submission as part of drug approval and post-marketing quality assurance. In tropical countries, stability studies are also aligned with climatic Zone IVb conditions (30°C/75% RH), reflecting higher temperature and humidity stress typical of regions such as India. Importantly, the expiry date does not signify a sudden transition to toxicity, but rather the point beyond which the manufacturer no longer assures labeled strength and stability. Available evidence suggests that many solid oral dosage forms, particularly tablets and capsules, exhibit considerable chemical stability beyond their printed expiry dates when stored under controlled conditions. Programs such as the U.S. FDA-supported Shelf Life Extension Program (SLEP), conducted for military medical stockpiles, have demonstrated prolonged potency for several drug classes under ideal storage. When no suitable alternative is available, outdated drugs may be effective.
V et al. (2026) studied this question.