Phases of Clinical Trials

Clinical trials are classified into phases, namely, Phase I, II, III, & IV. In Phase I, few volunteers participate, and in the next three phases, a large number of volunteers are involved.

The phases are the steps in which the scientists perform the investigation with a health intervention to find enough evidence for the process which could be useful as a medical treatment.


Phase I

It involves only a few healthy, willing volunteers (20 to 100) to carry out the clinical trial. The initial month of testing can take several months to complete. The study is framed to determine the effects of drugs or devices; how the person reacts to the treatment provided. The rate of absorption, excretion, and metabolized are observed, and the side effects of increased dosage are monitored. Nearly 70% of experimental drugs pass this phase of testing.


Phase II

It studies the efficacy of a drug or device. Several hundreds of volunteers participate in this phase. The second phase of testing can last from several months to two years. Phase II is random trials wherein one group is administered an experimental drug, and the second group receives standard treatment or placebo. The studies are blinded, and so neither the physician nor the researchers know who has received the experimental drug. The same lab tests are carried on both the groups and the reports, and volunteer's reactions are studied. It allows investigators to provide the pharmaceutical company and FDA about the experimental drug efficacy of the new drug. About 1/3 of experimental drugs pass the phase I and phase II studies.


Phase III

It is to evaluate how the new medication works in comparison to existing drugs for the same condition. It involves up to 3000 participants who are in the state to get treated by the new medication. Phase III trials last up to several years. The purpose of phase III is to evaluate that modern medicine is better and safe than the ones existing in the market for the same condition. The process of randomization is used wherein one group is given new medication and the other group existing medication. The trial is double-blind where neither the participants nor the investigator knows who is on which drug. That eradicates being biased, and the report is justified. Once the investigator confirms the efficacy and safety of a product, FDA approves to launch in the market for the general mass.

Phase IV

Clinical trials come into force once the FDA has approved the drug.  This phase involves thousands of volunteers and can sustain for several long years. In this phase the investigators will elucidate more information about the safety and efficacy of the product in the long term.


Clinical trials and the different phases of studies by the investigators provide enough time to conclude its veracity and the safety of the product, which can be safely used on the general public.