The first step in testing an experimental drug in humans. Phase I trials evaluate the drug's safety and toxicity at different dose levels and determine drug pharmacokinetics. Because little is known about the possible risks and benefits of the drug being tested, Phase I trials usually include only a small number of participants (20 to 80). Testing of other biomedical interventions, such as diagnostic tests or medical devices, also begins with Phase I trials.
See Related Term(s): Clinical Trial, Pharmacokinetics, Phase II Trial, Phase III Trial, Phase IV Trial