Study Phase Definitions
Phase I Trials - Safety. The first time an experimental drug will be used in humans. The purpose of a Phase I trial is to assess the initial safety of the drug, as well as the metabolism, absorption, elimination and other drug activities, the preferred mode of drug administration (topical, IV, oral, etc.) and safe drug range. Usually trials are conducted on healthy volunteers
Phase II Trials - Dosage. The purpose is to explore the effectiveness of different dosage schedules for a research treatment following safety evaluation in a Phase I trial. Trials are usually conducted on patients.
Phase III Trials - Efficacy. The purpose of a Phase III trial is to assess a drug's effectiveness (efficacy) and safety compared against a suitable placebo or best current treatment or to determine the optimum dosage level for the treatment of a specific condition in a specific group of patients. These studies are randomized, intervention allocation and measurement is usually masked form study participants and investigators.
Other Trials - Any prospective comparative study involving human participants and the administration of a treatment or type of management, including diagnosis or the provision of lifestyle (e.g. dietary) advice.