What is done in phase 3 of drug development?

• A. Early pharmacology studies in animals.
• B. Single-center small patient studies.
• C. Large scale, multi-center clinical studies performed with final dosage form to determine safety and efficacy; side effects and toxic effects are monitored.
• D. Post-marketing surveillance only.

Answer: (C)

In phase 3 trials, researchers conduct large-scale, multicenter studies to confirm a drug’s safety and efficacy using the final dosage form. These trials enroll diverse, real-world patient populations and are designed to provide robust evidence by typically using randomized and controlled designs that compare the new drug to placebo or standard therapy. They monitor effectiveness and a broad range of adverse effects over longer periods, capturing data on benefit-risk balance that is strong enough for regulatory approval and labeling decisions.

This phase comes after initial safety and dosing studies and before any post-marketing work. The other options describe earlier-stage work (preclinical animal studies) or smaller early human studies, or post-approval surveillance, which occur after phase 3.