Introduction

The chemical stability of a drug in the desired dosage form is of great importance since therapeutic problems may result from poor drug stability. The net result of drug instability is that the patient does not receive the proper dose of the active drug entity, and therefore, the full therapeutic effect of the drug is not realized. Additionally, drug decomposition may yield toxic by-products which endanger the patient.

The industrial pharmacist must choose dosage form excipients and storage conditions that result in an acceptable fraction (generally 90-95% or greater) of the drug being present for an acceptable length of time. The hospital or retail pharmacist must observe the manufacturers' storage recommendations. He/she must also be aware of the types of degradation that a particular drug is subject to since drug products are frequently repackaged at the time of dispensing.