Background:

Enalapril (MK-421) is an angiotensin converting enzyme (ACE) inhibitor.

Enalapril (MK-421) belongs to a class of medications called angiotensin converting enzyme inhibitors. Normally angiotensin I is converted to angiotensin II by angiotensin converting enzyme (ACE). Angiotensin II constricts blood vessels, increasing blood pressure. By inhibiting ACE, Enalapril (MK-421) decreases levels of angiotensin II leading to less vasoconstriction and decreased blood pressure[1].

[1]. http://en.wikipedia.org/wiki/Enalapril