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Different Phases of Clinical Trials

Medical clinical trials plays an important role in development of new drugs. These trials are conducted in three phases.


Clinical trials are a means of developing new treatments and medications for diseases and conditions. There are strict rules for clinical trials, which are monitored by the National Institutes of Health and the U.S Food and Drug Administration. Clinical trials are also called clinical studies, research protocols or medical research and often compare one drug against another to see which is more effective, or the medicine or procedure in a specific demographic group or for a specific disease.

About Clinical Trials

Why Participate in a Clinical Trial?

Participants in clinical trials can play a more active role in their health care, gain access to new research treatments before they are widely available and help others by contributing to medical research.
Where Do the Ideas for Trials Come from?

Ideas for clinical trials usually come from researchers. After researchers test new therapies or procedures in the laboratory and/or in animal studies, the treatments with the most promising test results are moved into clinical trials. During a trial, more and more information is gained about a new treatment, its risks and how well it may or may not work.

Who Sponsors Clinical Trials?

Clinical trials are sponsored or funded by a variety of organizations or individuals such as physicians, medical institutions, foundations, voluntary medical-related groups and pharmaceutical companies, in addition to federal agencies such as the National Institutes of Health, the Department of Defense and the Department of Veteran’s Affairs. Trials can take place in a variety of locations, such as hospitals, universities, doctors’ offices or community clinics.

What is a Protocol?

A protocol is a study plan on which all clinical trials are based. The plan is carefully designed to safeguard the health of the participants as well as answer specific research questions. A protocol describes what types of people can participate in the trial; the schedule of tests, procedures, medications and dosages; and the length of the study.

While in a clinical trial, participants following a protocol are seen regularly by the research staff to monitor their health and to determine the safety and effectiveness of their treatment.

What is a Placebo?

A placebo is an inactive pill, liquid, or powder that has no treatment value. In clinical trials, experimental treatments are often compared with placebos to assess the treatment’s effectiveness. In some studies, the participants in the control group will receive a placebo instead of an active drug or treatment.

What is a Control or Control Group?

A control is a standard by which experimental observations are evaluated. In many clinical trials, one group of patients will be given an experimental drug or treatment, while the control group is given either a standard treatment for the illness or a placebo.

What are the Different Types of Clinical Trials?

Treatment trials test new treatments, new combinations of drugs, or new approaches to surgery or radiation therapy.

Prevention trials look for better ways to prevent disease in people who have never had the disease or to prevent a disease from returning. These approaches may include medicine, vitamins, vaccines, minerals or lifestyle changes.

Screening trials test the best way to detect certain diseases or health conditions. Quality of Life trials (or Supportive Care trials) explore ways to improve comfort and the equality of life for individuals with a chronic illness.

Classification of Clinical Trials

There are three types of clinical trials – phase I, phase II and phase III – each one is designed to learn something different about a new medical treatment.

Phase I Trials

A phase I trial is the first test of a new treatment, and it uses the fewest number of patients (20-30 patients is typical). A phase I trial for a new drug is designed to determine the safety of the new drug, how to best administer it and the correct dosage (i.e., one that will minimize undesirable side effects). Because investigators are very interested in how the drug behaves in the body, patients in a phase I trial undergo frequent monitoring of their vital signs. Although drugs being tested in a phase I trial have shown promise in the laboratory, there is no guarantee that the drug will have any positive effects on a patient.

Patients participating in a phase I drug trial help advance basic medical knowledge; they may or may not reap any personal benefits.

Phase II Trials

After a phase I clinical trial has determined the safe dose of a drug, it can enter a phase II trial, which begins the process of determining the drug’s effectiveness in treating a specific type of disease. Because a phase II trial involves more patients than a phase I trial, physicians also have a chance to observe any less common side effects associated with the drug. In a phase II trial, which can involve 100 patients or more, physicians carefully monitor patients for a drug effect. For example, in a clinical trial testing a drug to increase the number of platelets in the blood, patients would have frequent blood samples taken, but they might also undergo several physical exams and other tests. The high level of patient monitoring in a phase II trial can be very time-consuming, so patients should take this into account when considering a phase II trial.

If a drug in a phase II trial brings about a positive change in at least one-fifth of the patients, then it can be tested in a phase III trial. However, if the new drug has shown very positive effects in patients, the FDA also has the option of approving the drug for general use at this point.

Phase III Trials

A phase III trial involves the largest number of patients, typically several hundred, even thousands of patients. Phase III trials are randomized, which means that some of the patients in the trail are randomly chosen to receive the experimental treatment, while the others receive a standard treatment. The outcomes of the patients receiving the new treatment (the treatment group) are compared with the outcomes of the patients receiving the standard treatment (the control group). In some phase III trials (single-blind studies), patients do not know which control group they are in. In a double-blind study, the physicians also do not know which patients are in the treatment group and which are in the control group. Blinded studies are used to prevent biased study results. If a new drug successfully passes a phase III trial, the FDA will approve the drug for marketing to the general public.

Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of pharmaguideline.com, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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2 comments: Post Yours! Read Comment Policy ▼

  1. phase IV study should also be included. guidelines describe in ICH and schedule y

  2. A very useful and well-written blog. This article is incredibly thorough, and the blog is well-written and filled with useful information. Wonderful work! complete clinical trial details with enlightening content. This article provides accurate information that promotes trustworthy and reliable information while clearly outlining the various stages of clinical trials. This allows for the enrolment of more people in clinical trials. Clinical trials are conducted to learn more about the medication's efficacy and safety. Share more content like this.


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