Clinical trials are medical research studies that show how scientific discoveries can be applied to patients. Volunteers undergo testing with the objective of clarifying the clinical, pharmacological and / or other pharmaco-dynamic effects, adverse reactions or to study the different changes produced in the body. In order to be able to participate in a trial, clinical trial managers must study the anatomy and physiology of the person to assess their suitability. Once the person is accepted for the study, a contract must be signed which details the possible adverse effects.