Analysis of multiple end points in consumer research in support of switching drugs from prescription to over-the-counter status: the concept of end-point hierarchies.

Clinical and regulatory decision making concerning over-the-counter (OTC) drugs requires research designed to understand how consumers will self-manage treatment using the candidate OTC drug. Consumer research for an OTC drug may include studies of label comprehension, self-selection, and actual use. Definition and analysis of end points for these trials have varied in the absence of consensus on optimal approaches. Research programs should prospectively prioritize the importance of label messages based on their roles in the safe and effective use of the drug. The assessment of messages for which failure to heed warnings will expose the consumer to increased risk or clinically relevant treatment failure should receive the highest priority as study end points. Based on the consequences of unheeded warnings, message-specific targets for appropriate response rates can be predefined. This prospective, hierarchical approach to end-point definition, combined with prespecification of targeted correct-response rates, has the potential to increase the scientific rigor and regulatory utility of these important research studies.