Clinical research is a branch of healthcare science that determines the safety and effectiveness (efficacy) of medications, devices, diagnostic products, and treatment regimens intended for human use.
These may be used for prevention, treatment, diagnosis, or for relieving symptoms of a disease. Clinical research is different from clinical practice. In clinical practice established treatments are used, while in clinical research evidence is collected to establish a treatment.
Clinical trials involving new drugs are commonly classified into four phases. Each phase of the drug approval process is treated as a separate clinical trial. The drug-development process will normally proceed through all four phases over many years. If the drug successfully passes through Phases I, II, and III, it will usually be approved by the national regulatory authority for use in the general population. Phase IV is 'post-approval' studies.
Phase I includes 20 to 100 healthy volunteers or individuals with the disease/condition. This study typically lasts several months and its purpose is safety and dosage.
Phase II includes a larger number of individual participants ranging 100-300,
Phase III includes approximately 1000-3000 participants to collect more data about the drug. 70% of drugs advance to the next phase.
The phase IV trial is also referred to as post-marketing surveillance and as the name suggests, it is conducted after the drug is already marketed and available to the general public. The main objective of the phase 4 trial is to check the drug's performance in real life scenarios, to study the long-term risks and benefits of using the drug, and to discover any rare side effects.