During which phase are large-scale studies conducted to confirm a drug’s efficacy?

Large-scale studies to confirm a drug's efficacy are conducted in Phase III of clinical trials. This stage follows the earlier phases, which primarily focus on assessing safety and determining the appropriate dosing. In Phase III, the drug is tested on a larger and more diverse population, which helps provide a more comprehensive understanding of its effects and effectiveness compared to existing treatments or placebos.

The primary goal of Phase III is to gather enough data to demonstrate that the drug's benefits outweigh any risks, thus supporting its potential approval for widespread use. This phase is crucial in the regulatory process, as it provides the evidence needed for pharmaceutical companies to submit a New Drug Application (NDA) to regulatory authorities, such as the FDA.

A significant aspect of Phase III includes randomized controlled trials and may involve multicenter studies to ensure varied demographic and clinical representation, further solidifying the drug's efficacy profile before it reaches the market.