Clinical trials are systematic studies carried out on human subjects to evaluate the safety, efficacy, pharmacological action, and adverse effects of new drugs before they are approved for marketing. These trials are conducted in different phases according to regulatory guidelines. Each phase has a specific objective and involves a different number of participants. The four phases of clinical trials are Phase I, Phase II, Phase III, and Phase IV. Phase I clinical trial is the first stage of testing a new drug in human beings after successful preclinical studies on animals. This phase is mainly concerned with the safety and tolerability of the drug. It is usually conducted on a small number of healthy volunteers, generally between 20 and 100 individuals. In the case of highly toxic drugs such as anticancer agents, patients suffering from the disease may be selected instead of healthy volunteers. The primary objective is to determine the safe dose range, route of administration, pharmacokinetics, and pharmacodynamics of the drug. Researchers study absorption, distribution, metabolism, and excretion of the drug in the body. The study also identifies common side effects