An adverse event is any unfavorable or unintended disease, sign, or symptom (including an abnormal laboratory finding) that is temporally associated with the use of a medical therapy or procedure. An adverse event may or may not be considered related to the medical therapy or procedure. Such events can be related to the therapy, dose, route of administration, patient, or caused by an interaction with another drug(s) or procedure(s).
Adverse events can occur both pre- and post-marketing approval. The U.S. Food and Drug Administration (FDA) has systems to report adverse events that may be associated with a therapy already available in the clinical setting.
ClinicalTrials.gov Glossary of Common Site Terms
U.S. Food and Drug Administration (FDA): What is a Serious Adverse Event?
MedWatch: The FDA Safety Information and Adverse Event Reporting Program