ACEI drugs are widely used in clinical practice, not only for the treatment of hypertension, but also for the treatment of heart failure, and are more widely used in clinical practice. Some patients are prohibited: 1, pregnant women: pregnant women can not be used because it can be teratogenic; 2, patients with hyperkalemia, which can lead to elevated blood potassium; 3, patients with low blood pressure: patients with normal blood pressure or less, can not use ACEI drugs; 4, patients with severe aortic stenosis, severe mitral stenosis is also not applicable to ACEI drugs. Because patients with aortic stenosis and mitral stenosis, the narrowing of the valve leads to a decrease in blood ejection from the heart to the whole body. At this time, the use of ACEI drugs lead to vasodilatation, the patient will appear hypotension, and even shock state, so this type of patients are not available; 5, patients with double renal artery stenosis; 6, patients with malformed kidney: the patient has only a single kidney, only a single kidney, isolated kidney, and isolated kidney and its renal artery stenosis, this type of patients are also not available ACEI drugs. When using ACEI drugs, be careful not to use them together with drugs that can lead to high potassium, such as aldosterone receptor antagonists, and ARB drugs such as sartan drugs, try not to use these two drugs together, because there is a risk of high potassium.