Captopril is used for:

Treating high blood pressure, heart failure, or certain diabetic kidney problems. It is used to improve survival and decrease heart failure in certain patients after a heart attack. It may be used alone or in combination with other medicines. It may also be used to treat other conditions as determined by your doctor.

Captopril is an angiotensin-converting enzyme (ACE) inhibitor. It works by decreasing a chemical that tightens blood vessels. This causes blood vessels to relax (dilate), which lowers blood pressure and decreases the workload on the heart...