In this book, we define "pharmaceuticals" as drug substances having pharmacological effects and the dosage forms containing these drug substances, which are intended for therapeutic use. Drug substances used at the present time range from small-molecular-weight chemicals to polymers such as proteins. In the future, products derived from genomic research will have to be included. Some drug substances are susceptible to chemical degradation under various conditions owing to their fragility of their molecular structure. Other drug substances undergo physical degradation changes rather than chemical degradation, leading to various changes in their physical state. Download disini