Which phase is initial human testing for pharmacokinetics and toxicity?

• A. Investigational New Drug (IND)
• B. Phase I Testing
• C. Phase II Testing
• D. New Drug Application (NDA)

Answer: (B)

Phase I testing is the initial human study focused on pharmacokinetics and safety. In this stage, a small group of volunteers (often healthy, or patients when appropriate) receives the drug to map how it is absorbed, distributed, metabolized, and excreted, and to identify acute toxicities and tolerability. The aim is to establish a safe starting dose and characterize the drug’s safety profile before moving to larger trials that assess efficacy. Regulatory groundwork includes an Investigational New Drug application to permit these studies, while a New Drug Application is submitted later to seek marketing approval after the larger trials confirm benefit and safety.