Which of the following phases generally involves a few patients with a medical problem a drug is intended to treat and is designed to determine both safety and efficacy of a drug?

• A. Phase I
• B. Phase II
• C. Phase III
• D. Phase IV

Answer: (B)

Phase II trials test how well the drug works in people who actually have the condition it’s meant to treat, while continuing to monitor safety. They involve a relatively small number of patients and aim to establish the effective dose range and early signs of efficacy, along with safety data. This stage follows Phase I, which focuses more on basic safety and dosing (often in healthy volunteers), and precedes Phase III, which enrolls many more patients to confirm efficacy and monitor adverse effects on a larger scale. Phase IV occurs after approval and looks at safety in the general population.