Captopril

Captopril is an angiotensin converting enzyme inhibitor. Under normal conditions, angiotensin converting enzyme converts angiotensin I into angiotensin II. Angiotensin II causes vasoconstriction, which raises blood pressure, stimulates the adrenal glands to secrete aldosterone and increase sodium and water retention, stimulates the sympathetic nervous system, and promotes hypertrophy of the myocardium and vascular smooth muscle. When captopril inhibits angiotensin converting enzyme, angiotensin II can no longer be produced, and these effects are therefore suppressed. In addition, angiotensin converting enzyme also participates in the breakdown of bradykinin, so inhibition of the enzyme may increase bradykinin levels and further influence the regulation of vascular tone.