Clinical research that is related to developing products for patient care is divided into two preclinical and four clinical phases, each addressing different questions. The knowledge gained at each phase is assessed before progressing to the next. The table below provides an overview of the process. Click each phase to learn more.

The beginning of Phase III marks a radical change in the development of a drug. The decision to start Phase III studies indicates a commitment on the part of the sponsor to increase expenses dramatically. The number and the size of the studies now increase. Studies may enroll several hundred to several thousand subjects and last for a year or longer. Subjects have the condition or disease being treated. Most Phase III studies are conducted at many sites in order to enroll enough subjects and control for errors. The same protocol is used at all the study sites, and investigators and their research staffs are trained to conduct the study uniformly. There are strict and lengthy SOPs. Questions to be answered during Phase III studies include the following: Phase III is the longest and most expensive segment of the clinical research process. To make sure that true and useful data are analyzed during. Phase III, it is important to continue careful monitoring of studies.

Phase III studies ask the questions:

• Is the drug or more effective than alternatives currently on the market or in development?
• Is the drug effective under unusual conditions? For example, is it effective for elderly subjects?
• Is it effective for subjects taking other medications?
• Is the drug effective for long periods of time?
• Do subjects develop tolerance to it?
• Is there an explanation for the times when the drug is not effective?
• Do subjects comply with the dosing and time schedules required for effectiveness?
• Does the previously established safety profile hold up in large groups of subjects and over long periods of time?
• With what other drugs does the drug interact?
• How does the drug interact with food?