Clinical trials are essential to the advancement of medical science, providing systematic methodologies for assessing the safety, efficacy, and therapeutic value of new drugs and medical interventions. This article presents a comprehensive overview of the phases of clinical trials— ranging from exploratory (Phase 0 and I) to confirmatory (Phase III) and post-marketing surveillance (Phase IV). Each phase is characterized by specific objectives, participant groups, and study designs. Various trial designs, including parallel, crossover, factorial, randomized withdrawal, and matched pairs, are discussed with an emphasis on their respective advantages and limitations. The article also reviews randomization methods such as simple, block, stratified, covariate adaptive, cluster, and split-body techniques, which are critical to ensuring unbiased results. Key terminologies, including open-label, single-blind, and double-blind studies, are defined to clarify study methodologies. Furthermore, the ethical dimensions of clinical research are explored through the evolution of major international guidelines such as the Nuremberg Code, Declaration of Helsinki, Belmont Report, and ICH-GCP. National regulations, particularly those established by the Indian Council of Medical Research (ICMR), are also highlighted. This review underscores the scientific, methodological, and ethical frameworks that guide clinical trial conduct, ensuring both data integrity and participant protection.
Raghunath Prabhu (2025) studied this question.