Captopril-induced renal damage

　　The cause of renal damage caused by methacrylate propanamide is related to the failure of clinical doctors to strictly grasp the indications for drug use. Patients with renal artery stenosis, renal artery thrombosis, solitary kidney, and excessive dosage of methacrylate propanamide are all prone to increase the risk of renal damage. The pathogenesis of renal damage caused by methacrylate propanamide may have the following aspects:

　　1, Changes in hemodynamics
　　Angiotensin II within the kidney can affect renal vascular tone, causing constriction of the afferent and efferent arterioles, leading to reduced renal blood flow, ensuring blood volume and maintaining blood pressure. Methacrylate propanamide blocks the formation of angiotensin II, reducing its effect. Compared with the afferent arteriole, the resistance of the efferent arteriole is reduced more significantly, resulting in reduced glomerular blood flow and decreased glomerular filtration rate, causing renal function damage. When there is renal artery stenosis, the glomerular blood flow decreases, and its glomerular filtration rate depends on the constriction of the efferent arteriole to maintain. After the use of methacrylate propanamide, the efferent arteriole is dilated, leading to a sudden decrease in glomerular filtration rate and causing acute renal failure.

　　2, The direct toxic effect of methacrylate propanamide on the proximal tubular epithelial cells
　　It may be related to the fact that methacrylate propanamide blocks the function of some key esterase in the proximal tubular epithelial cells, or methacrylate propanamide may hinder the recovery of cells after ischemia, aggravate cellular damage after reperfusion, and thus lead to acute tubular necrosis.

　　3, Allergic factors and immune regulatory function disorder
　　It may be related to the post-drug allergic reaction, which causes infiltration of monocytes and lymphocytes in the renal interstitium and the release of some cytokines (such as interleukin-1, interleukin-2, tumor necrosis factor-α).

　　Due to the damage to renal function, creatinine and urea nitrogen excretion are blocked in methacrylate propanamide-induced renal damage. Therefore, in clinical practice, renal function tests show increased creatinine and urea nitrogen, and in severe cases, creatinine levels may appear that indicate renal failure. At the same time, due to the decreased potassium secretion function of the kidneys, potassium cannot be excreted from the blood, which may cause hyperkalemia. In severe cases, it can directly lead to cardiac arrest.

　　The symptoms of methacrylate propanamide-induced renal damage include renal manifestations and extrarenal manifestations. The specific clinical manifestations are as follows:

　　First, renal manifestations
　　1, Acute renal failure: Mild cases may show accidental discovery of renal function decline, asymptomatic increase in blood creatinine, increase by more than 100μmol/L, decreased intrinsic creatinine clearance, and glomerular filtration rate may decrease by 50%. In patients with renal artery stenosis, especially those with bilateral renal artery stenosis, sudden oliguria or anuria may occur, and renal function may deteriorate rapidly in a short period of time, which may manifest as acute renal failure.
　　2, Acute interstitial nephritis: Clinical manifestations include proteinuria, generally less than 2g/24h. In addition, there are renal glycosuria, rash, and increased eosinophils in the blood.
　　3. Nephrotic syndrome: manifested by massive proteinuria, hypoalbuminemia, accompanied or not accompanied by hyperlipidemia and edema, with possible hypertension. Renal biopsy shows membranous nephropathy.

　　Second, extrarenal manifestations
　　May include cough, hyperkalemia, increased urine sodium, etc.

　　The causes of methyldopa-induced kidney damage are related to the failure of clinical doctors to strictly control the indications for medication. Therefore, clinical doctors should pay attention to the following aspects:

　　1. Strictly control the indications for medication
　　Before taking the drug, it is necessary to clarify whether there are any risk factors, such as renal artery stenosis, renal硬化, renal artery thrombosis, especially severe bilateral renal artery stenosis and solitary kidney. If the above conditions exist, methyldopa should be used with caution or contraindicated.

　　2. Pay attention to observation and timely discontinuation of medication
　　During the first week of taking methyldopa, renal function should be closely monitored and routine urine and blood potassium levels should be checked. If renal function deterioration is found, the drug should be discontinued promptly and renal function should be rechecked in the short term. It is usually complete recovery after discontinuation of the drug.

　　In the blood and urine tests of methyldopa-induced kidney damage, proteinuria, glycosuria, increased urine sodium, elevated blood urea nitrogen, increased creatinine, decreased内生肌酐清除率, decreased glomerular filtration rate, and increased eosinophils can be seen.
　　Histopathological examination: Under the light microscope, renal tubular epithelial cell degeneration and necrosis can be seen, and interstitial inflammation cell infiltration is mainly mononuclear and lymphocytes, with some neutrophils and eosinophils. Some patients have glomerular lesions, which are mostly manifested as membranous nephropathy. Under the electron microscope, spherical electron-dense deposits are seen in the epithelial cells of the glomerular capillary basement membrane.

　　For methyldopa-induced kidney damage, it is recommended to choose a diet with high-quality low-protein, high-vitamin, low-salt, and low-potassium foods. It is necessary to avoid foods high in potassium, such as bananas, tangerines, jujubes, etc., as they can cause certain damage to the kidneys.

　　Patients with methyldopa-induced kidney damage can stop taking the drug and relieve the symptoms spontaneously. It is generally not recommended to use hormone or cytotoxic drugs. In case of acute renal failure, active treatment should be given. A few patients with severe acute renal failure caused by methyldopa, persistent oliguria or anuria for more than 3 days, or abrupt deterioration of renal function require emergency hemodialysis or peritoneal dialysis.