Читать книгу The SAGE Encyclopedia of Stem Cell Research - Группа авторов - Страница 411

All new medical procedures or pharmacological substances go through a series of clinical trials, comprising a four-stage process of testing how safe a clinical intervention is and how it is to be used. The stages of clinical trials test different aspects of usability and safety of a drug for patients. The first stage is called a phase I trial, which is used to evaluate the safety of a new clinical method or drug; typically this is conducted in a small group of people. This may include healthy, unhealthy, or a combination of both, used to evaluate any side effects and determine the right dosage. The next stage is a phase II trial, which is aimed at testing the clinical procedure or drug that has passed through stage I on a larger group of people; often ill people are used in this stage of the trial to evaluate how effective the new procedure or drug works in people with the target condition and how well it works in a controlled, short period of time. The middle stage is a phase III trial, designed only for the drugs that are deemed successful in phase I and II trials. Again the procedure or drug is tested on a large number of ill individuals, and the outcome is compared to existing intervention for the target condition or placebo drug in the case of a drug trial. This trial allows researchers to determine whether the new drug or approach works better than the existing ones for the target condition, while evaluating any clinically significant side effects. Finally, in some cases, a last stage is conducted. Phase IV trials are conducted on drugs and procedures that are successful in the first three trial stages and a marketing license is given for the drug. With a marketing license, the drug can be given to patients. This phase allows the further understanding of the safety, side effects, and effectiveness of the drug while it is used in normal clinical practice.