Which phase tests safety and pharmacokinetics in healthy volunteers to determine safety and likely dose?

• A. Phase 0
• B. Phase 1
• C. Phase 2
• D. Phase 3

Answer: (B)

Phase 1 trials focus on safety and how the drug behaves in the body. They enroll healthy volunteers to assess safety, tolerability, and pharmacokinetics—how the drug is absorbed, distributed, metabolized, and excreted. This phase uses small dose-escalation studies to determine a safe starting dose and how exposure changes with dose, which helps set the initial dosing for later trials. The other phases have different aims: Phase 0 uses micro-dosing to gather early PK data; Phase 2 tests efficacy and safety in patients to refine dosing; Phase 3 confirms efficacy and safety in larger populations to support approval.