What kind of subjects are typically examined in Phase I trials?

Phase I trials are primarily focused on assessing the safety, tolerability, pharmacokinetics, and pharmacodynamics of a new drug in humans for the first time. Typically, these trials are conducted with healthy volunteers rather than patients with specific diseases. The main goal is to evaluate how the drug behaves in the human body, including how it is absorbed, metabolized, and excreted.

Using healthy volunteers allows researchers to minimize potential confounding factors that could arise from underlying health conditions. This population is more capable of providing baseline data regarding how the body reacts to the investigational drug without existing medical issues that might influence the results. Hence, healthy volunteers are the standard participants in Phase I trials.

In contrast, patients with chronic diseases, individuals with drug dependency, and high-risk patient populations would generally be recruited for later-phase trials (Phase II or Phase III), where efficacy and therapeutic benefit are evaluated in the context of the specific conditions those populations face. This structured approach allows for a clear and effective assessment of both safety and biological response specifically in patients who require treatment, after initial safety profiles have been established in healthy volunteers.