Prazosin is an antihypertensive derived from quinazoline which belongs to the class of alpha-blockers. Prazosin is used to lower blood pressure by relaxing blood vessels. This action is due to the fact that prazosin is selective for alpha1 receptors on vascular smooth muscle. These receptors are responsible for the vasoconstrictive action of norepinephrine, which is responsible for raising blood pressure. Because of these effects, prazosin is indicated in the treatment of high blood pressure, anxiety and post-traumatic stress disorder and panic disorder.

A clinical study has begun to determine the potential of prazosin to slow and possibly prevent one of the worst effects of Covid-19, cytokine storm. This study was based on research in mice that showed that prazosin could prevent this cytokine storm phenomenon, as well as a study of a cohort of patients suffering from acute respiratory distress from a variety of causes.