ABSTRACT
Drug substances and drug products are required to be physically and chemically stable under recommended storage conditions. Most drugs are susceptible to chemical decomposition in their dosage forms. Degradation can lead to loss of the drug’s potency and generation of impurities in drug products. Regulatory guidelines require identication, quantitation, and/or toxicological evaluation of impurities in drug products when they exceed a given threshold, which depends on the drug’s daily dose. In addition to the time and cost associated with these investigations, if an impurity is found to be signicantly toxic, it can compromise a drug development program. Therefore, impurities are sought to be controlled in drug products by understanding of the rates and mechanisms of drug degradation reactions, and implementing stabilization strategies. For example, knowledge of the rate at which a drug deteriorates under various conditions of pH, temperature, humidity, and light allows formulators to choose a vehicle that will retard or prevent drug degradation. Chemical kinetics deals with rates of chemical reactions. A knowledge of reaction kinetics under various conditions helps identify mechanisms of drug degradation and stabilization.
