What is the primary purpose of Phase I clinical trials in drug development?

The primary purpose of Phase I clinical trials in drug development is to assess the safety of a drug. During these trials, researchers administer the drug to a small group of healthy volunteers or sometimes to patients with specific conditions to closely monitor any adverse effects and ensure that the drug is safe for human use. The focus is on determining how the drug behaves in the body, including pharmacokinetics (how the drug is absorbed, distributed, metabolized, and excreted) and to understand safe dosage ranges.

Phase I trials do not evaluate long-term effects, as they typically involve short-term observation during a limited timeframe. They also do not aim to determine the efficacy of the drug in larger populations or through market research, as those aspects are generally explored in later phases of clinical trials. Thus, the emphasis in Phase I is squarely on safety for initial human trials, making the understanding of this phase crucial in the entire drug development process.