Introduction
The Food and Drug Administration (FDA) is a branch of the U.S. Department of Health and Human Services. It regulates a variety of commercial articles intended to affect the structure or function of the body, human or animal. Its federal regulatory power derives from the Interstate Commerce Clause. Rooted in the early 20th century USDA Bureau of Chemistry, FDA is guided today by the Food, Drug, and Cosmetics Act (FDCA).
Several branches of FDA are significant to the daily practice of medicine. One, in particular, the Center for Drug Evaluation and Research, is responsible for ensuring the safety and efficacy of drugs in the marketplace.
A short description of the drug approval process follows.
Preclinical
Prior to approaching FDA, entities conduct research on candidate substances. Potentially important candidate drugs are thoroughly studied (1) in vitro for pharmacokinetic profile and (2) in vivo in two different species for toxicity and efficacy. Promising compounds are pursued with an Investigational New Drug application, which is essentially requesting an exception from being found in violation of the FDCA. The IND requests permission to being human trials, and includes provisions satisfying other key requirements like IRB approval and Informed Consent.
Phase One
This testing aims to evaluate the toxicity profile of candidate compounds. Usually healthy volunteers are given the drug and are followed for signs and symptoms of toxicity. There is also some pharmacodynamic data gathered at this stage, but primarily the safety profile is studied. Some compounds like chemotherapeutic agents do not need to go through this phase. This phase investigates toxicity at varying doses.
Phase Two
This stage evaluates the efficacy of the candidate compound in a cohort of people with the disease or condition for which treatment is sought. These studies are usually compared to placebo and utilize randomization in the study design. Safety is continually examined throughout the clinical trial process, and here is studied in a larger population of "unhealthy" people. Further, optimal dosing is studied at this stage of testing.
Phase Three
This phase examines the candidate drug on larger cohorts in randomized, often multicenter, clinical trials. They are designed the study efficacy and safety, as well as dosing. Data from this and all previous studies are compiled into a New Drug Application to market the drug for the indication(s) studied.
Phase Four
This is a post-approval stage that is not strictly required (except for all fast-tracked drugs). This testing involves continuing to monitor the safety profile of the drug, as well as to study new indications and efficacies.