Angiotensin-converting enzyme inhibitors (ACEI) are largely similar to other antihypertensive drugs in lowering blood pressure, but their clinical use is becoming more widespread due to their good tolerability, fewer side effects, apparent metabolic channel selectivity, and beneficial effects based on something other than antihypertensive effects, such as organ protection, and there have been numerous clinical studies confirming that ACEI have renal The renal protective effect of these drugs is mostly in renal diseases with proteinuria, which is achieved by lowering urinary protein, and restricting sodium intake and using appropriate diuretics can increase the effect of lowering urinary protein and delay the progression of chronic kidney disease. Its cardiovascular protective effect is mainly to reduce intima-media thickness, improve arterial vascular compliance, endothelial function and reduce left ventricular hypertrophy, reduce the incidence of coronary heart disease, myocardial infarction and heart failure. A large amount of evidence-based medical evidence shows that ACEI use in patients with hypertension, myocardial infarction and heart failure can significantly reduce the rate of death, prolong life expectancy and reduce the incidence of cardiovascular and cerebrovascular events, which has important clinical significance. However, ACEI drugs can lead to the occurrence of hyperkalemia because of the inhibition of aldosterone release. Due to the dilatation of the small glomerular efferent arteries and the reduction of glomerular filtration pressure, the glomerular filtration rate can be reduced to varying degrees, resulting in a variable degree of elevated blood creatinine, especially in patients with underlying renal insufficiency or heart failure, therefore, they should be used with caution in patients with cardiac and renal impairment. It should be used with caution in patients with cardiac or renal impairment. In addition, it should be prohibited in patients with bilateral renal artery stenosis or isolated kidney with renal artery stenosis. 1, Renal insufficiency Usually, ACEI drugs are safe to use in patients with CKD and mildly reduced renal function, but they must be used at low doses to start with, and then carefully increase the dose according to the condition based on monitoring renal function and changes in blood potassium concentration. ACEI is best used in drugs that are excreted via both hepatic and renal channels. Studies have shown that in patients with hypertensive renal impairment or diabetic nephropathy, the addition of ACEI can significantly delay further deterioration of renal function, regardless of their pre-treatment blood creatinine levels, as long as they can be successfully added. However, for patients who already have renal impairment and need to be treated with ACEI, in order to avoid or mitigate the rise of blood creatinine after medication, a small dose should be used to start and should be administered under the close observation of a physician. Even for patients who have been treated with ACEI for a long time, when the blood creatinine level is greater than 3mg/dl, such drugs should be avoided as much as possible without close monitoring by a specialist physician. 2, Blood potassium ACEIs are prone to hyperkalemia when combined with potassium-preserving diuretics or oral potassium supplementation. Therefore, ACEI drugs should be avoided with potassium-storing diuretics, potassium-replenishing drugs and non-steroidal anti-inflammatory drugs, and if the patient must take potassium supplementation at the same time, the dose of potassium supplementation should be reduced and the changes in blood potassium should be closely monitored. To prevent the development of hyperkalemia, close monitoring of renal function and changes in blood potassium concentration is required between 4 and 12 weeks of ACEI-like drugs in all patients with a GFR of 4.5 mmol/L. 3, First-dose hypotension First-dose hypotension is also a common adverse effect of ACEI drugs, especially in elderly, hypovolemic and heart failure patients. The occurrence of first-dose hypotension is not associated with allergic reactions or the efficacy of future ACEI applications. To avoid the occurrence of first-dose hypotension, it is recommended to start with a small dose (e.g., captopril 3.125 mg to 6.25 mg), and in patients who are also using diuretics, the application of diuretics should be suspended or reduced before the addition of ACEI. 4, other problems ACEI use early can appear transient proteinuria, generally does not affect the treatment, with the use of the drug for a longer period of time, the excretion of proteinuria can be reduced or disappear. In fact, ACEI can significantly reduce urinary microalbumin excretion in patients with hypertensive renal impairment or diabetic nephropathy. In addition, there is a risk of acute renal failure with ACEI analogues in elderly patients, in patients with hypovolemia, in patients with heavy diuretic use or in patients with cardiac failure; therefore, care must be taken to try to correct some clinical risk factors before using ACEIs.