Drugs used in medicine generally are divided into classes or groups on the basis of their uses, their chemical structures, or their mechanisms of action. These different classification systems can be confusing, since each drug may be included in multiple classes. The distinctions, however, are useful particularly for physicians and researchers. For example, when a patient experiences an adverse reaction to a drug, these classification systems allow a physician to readily identify an agent that has comparable efficacy but a different structure or mechanism of action. Likewise, knowledge of a drug’s chemical structure facilitates the search for new and potentially ...(100 of 9029 words)