Prazosin is an antagonist of α1-adrenergic receptors (α1-ARs). The affinity estimates (pKi) for inhibition of [3H]-prazosin binding to CHO-K1 cells expressing cloned human α1A, α1B and α1D adrenoceptors are 9.0, 9.9 and 9.5 respectively. It also inhibits α2-ARs with Ki values of 340 nM and 3.7 nM in α2A-AR expressing HT-29 cells and α2B-AR expressing NG108 cells respectively. It is used in the treatment of hypertension, anxiety and post-traumatic stress disorder. It is in clinical trials to prevent cytokine storm in patients with COVID-19.