Captopril is also used to improve survival and reduce the risk of heart failure after a heart attack in patients with a heart condition called left ventricular hypertrophy (enlargement of the walls of the left side of the heart). Captopril is also used to treat kidney disease (nephropathy) caused by diabetes in patients with type 1 diabetes and retinopathy (eye disease). Captopril belongs to a class of medications called angiotensin-converting enzyme (ACE) inhibitors. It decreases certain chemicals that tighten the blood vessels, so blood flows more smoothly and the heart can pump blood more efficiently.