Pharmacovigilance

Pharmacovigilance is the science and practice of detecting, assessing and understanding adverse effects of medicines and health products once they are in use.

Clinical trials involve limited numbers of people for limited periods, so rare, delayed or interaction-related harms often surface only after a product reaches the market. Pharmacovigilance systems collect reports from clinicians, manufacturers and consumers, look for patterns known as safety signals, and feed findings back into labeling changes, warnings or recalls. In the United States the FDA runs the MedWatch program and the FDA Adverse Event Reporting System, and manufacturers of approved drugs are legally required to report serious adverse events.

For cannabinoids, pharmacovigilance data come from the approved cannabidiol seizure medicine, where liver enzyme elevations and somnolence were identified, and from poison-control and adverse-event reports about consumer hemp products. Dietary supplement makers must report serious adverse events to the FDA, and consumers can file their own reports. Reports show association rather than proof of cause, but they are the main way safety knowledge grows after approval.