How many phases are in a clinical trial of a new drug?

A clinical trial of a new drug typically consists of four distinct phases, each designed to investigate different aspects of the drug's safety and efficacy.

In Phase 1, the drug is administered to a small group of healthy volunteers to assess its safety, determine dosage levels, and identify any side effects. This phase focuses primarily on the pharmacokinetics and pharmacodynamics of the drug.

Phase 2 expands the study to a larger group of participants who have the condition that the drug aims to treat. This phase evaluates the drug’s efficacy and further assesses its safety, often using a control group for comparison.

In Phase 3, the drug is tested on an even larger population to confirm its effectiveness, monitor side effects, and compare it to commonly used treatments. This is usually the final step before seeking regulatory approval, providing comprehensive data on the drug's overall benefit-risk profile.

Finally, after regulatory approval, Phase 4 occurs. This phase involves post-marketing surveillance, where long-term effects and safety are studied in the general population. However, this phase is not always included in the counting of phases as it is more about ongoing assessments rather than the initial testing of the drug's safety and effectiveness.

Each phase plays a crucial role in the drug development