ACE inhibitors are a classification of drugs used to treat high blood pressure and other associated problems. ACE inhibitors relax the muscles responsible for contracting blood vessels, allowing the blood vessels to dilate. By causing this dilation of the blood vessels, ACE inhibitors lower blood pressure, reducing the strain on the heart and kidneys.

The "ACE" in ACE inhibitors stands for angiotensin converting enzyme. This enzyme occurs naturally in the body. The enzyme acts to raise blood pressure by activating the angiotensin chemical. ACE inhibitors prevent this enzyme from activating the chemical, thereby keeping the angiotensin chemical from raising the blood pressure.

A wide variety of problems can be treated with ACE inhibitors. Hypertension (high blood pressure), congestive heart failure, kidney problems associated with diabetes, and other heart conditions are all commonly treated with ACE inhibitors. Common ACE inhibitors include quinapril, lisinopril, benazepril, and ramipril, but there are many others. All ACE inhibitors have similar methods of action within the body, and all are generally well tolerated by most patients.

ACE inhibitors are often helpful for patients with heart disease or heart failure. By lowering blood pressure, ACE inhibitors reduce strain on the heart and help prevent further heart damage or heart attack in patients with an already weakened heart. Similarly, patients who experience kidney problems as a result of diabetes often benefit from the use of ACE inhibitors. Because ACE inhibitors themselves can cause kidney problems in some patients, they are not right for all patients with kidney disorders.

Common side effects include cough, dizziness, abnormally low blood pressure (hypotension), headache, drowsiness, kidney problems, and elevated levels of blood potassium. Patients taking potassium supplements or drugs that can increase levels of potassium should consult their doctor before taking ACE inhibitors, since the medication can also increase potassium levels. Women who are pregnant or may become pregnant should not use ACE inhibitors because they can lead to birth defects. Despite these side effects and contraindications, ACE inhibitors can be very successful in treating a number of conditions associated with high blood pressure.