Which of the following is a primary source of drug information?

A primary source of drug information is characterized by original research or firsthand accounts that provide direct evidence or data. Clinical trial reports fit this definition as they present the findings from experimental research conducted on new drugs or treatments. These reports detail the methodology, results, and conclusions drawn by researchers, offering a comprehensive look into the drug's efficacy and safety, making them a crucial resource for healthcare professionals.

In contrast, other options like The Merck Manual and the Drug Product Database serve as compilations or summaries of information that have been gathered from various studies and reports, thereby classifying them as secondary sources. Chemical abstracts, while informative, also summarize the research findings from various studies rather than presenting original research themselves. Thus, they do not qualify as primary sources.