Introduction

According to a recent report to the nation issued by the Center for Drug Evaluation and Research (CDER) of the United States Food and Drug Administration (FDA), 215 prescription drugs and 71 over-the-counter drugs were recalled in the fiscal year of 2004 (CDER, 2004). The top five reasons for drug recalls in the fiscal year of 2004 were (a) current good manufacturing practice (cGMP) deviations, (b) subpotency, (c) stability data not supporting expiration date, (d) generic drug or new drug application discrepancies, and (e) dissolution failure. As indicated in the CDER Report to the Nation, a drug product must be recalled owing to a problem occurring in the manufacture or distribution of the product that may present a significant risk to public health. These problems usually but not always occur in one or a small number of batches of the drug product. Drug stability plays a very important role in pharmaceutical research and development. For a newly developed drug product, stability analysis not only provides useful information regarding the degradation of the drug product, but also determines an expiration dating period of the drug product. For the purpose of safety and quality assurance, most regulatory agencies such as the FDA require that an expiration dating period be indicated on the immediate container label for every drug product on the market.