Clinical trial is a systematic study of new drugs in human subjects to generate data for discovering/verifying clinical, pharmacological (Pharmacokinetic or pharmacodynamic) or adverse effects & to determine safety and efficacy of the new drug.

In simple words, a highly standardized scientific test of therapy, drugs or devices on groups of patients. The studies are performed under strict government regulations to prevent any harm to patients and it also has significant data to support the fact that the drug under investigation will prove beneficial to the patients.

There are four main components to any clinical trial, all considered to be a part of the protocol:

1. Disease, illness or condition: The experiment is developed and carried out on people with the same set of symptoms, who have had similar results on diagnostic tests, are determined to have the same or similar diagnosis, and perhaps are considered in similar stages of a disease. Which of these criteria are used depends on the purpose of the trial.
   
   For example, a trial may be undertaken with a group of patients who are all considered to have stage three lung cancer. Or, a study may be done on patients who have recently developed macular degeneration.


2. Purpose: There are several types of trials:
   
   Treatment trials probably account for the most clinical trials, test new drugs, therapies, devices, or surgeries.
   
   Prevention trials test the possibilities for keeping someone from developing a specific disease or condition.
   
   Diagnostic and Screening trials may result in new ways to detect or diagnose a specific disease or condition.
   
   Quality of Life trials also called Supportive Care trials are intended to study ways to keep people with difficult or chronic disease comfortable or to improve their quality of life.


3. Patients: One important aspect of developing evidence is making sure the patients meet consistent criteria. The more similar the participants, the more specific the outcomes can be. Depending on the trial, they may need to be the same gender, of similar ages, from the same race, have other similar genetic makeup, and have the same diagnosis with specific symptoms.
   
   For example, a drug could be tested on post-menopausal women with heart disease and yield excellent outcomes, but may not be a good choice for men of any age who have heart disease accompanied by diabetes.


4. Phases: There may be up to four phases of any clinical trial, and each phase is the next step in determining the outcomes. If or when problems arise in a phase, then the trial must be adjusted before it can move up to the next phase. In some cases, when real problems are demonstrated (e.g. if people get sicker or die) then the trials may be stopped.
   
   In Phase I trials, a small group of 20 to 80 people will be studied to evaluate the therapy being studied to make initial safety determinations, such as dosage amount and/or side effects.
   
   In Phase II trials, a larger group (up to 300 people) will be studied for the same reasons as Phase I trials.
   
   In Phase III trials, an even larger group (up to 3,000 people) will be studied to confirm the effectiveness of the drug, therapy or device being tested, monitor side effects, compare it to other treatments previously studied, and in general follow participants to confirm the treatment is safe. If a treatment is being studied and is found to be useful and successful through Phase III trials, it will be most often be submitted to the Regulatory Body for approval. If approved, will be marketed and sold.
   
   Phase IV trials are sometimes requested by the Regulatory Bodies to be run after the treatment has been marketed for some period of time, to confirm the patients using that therapy, post-approval, are finding the same results as were reported from the first three phases of trials, and reported through the application process to the Regulatory Body.

People participating in clinical trials have access to experimental medications or devices before they become available to the general public. If you participate, you may receive careful medical attention including examinations and tests at no cost. In some cases, you may be reimbursed for your time and expenses, such as travel or wedges.

You are helping others with the same disease, both now and in the future. You play an active role in your own health care.

If you have a disease that cannot be treated with an existing drug or regimen, participation might provide you with a successful treatment before it becomes available to others.

Some patients have no alternatives for treatment and permanent debilitation or death is imminent. In such cases, participation in a clinical trial may give them hope or possibilities that do not exist otherwise.