Why do diuretics cause side effects? How to limit the side effects of diuretics?

Posted by Pharmacist Pham Thi Kim Dung - Vinmec Times City International General Hospital

Diuretics have the effect of reducing water and salt reabsorption, increasing urine output and increasing salt excretion. Diuretics are often used in the treatment of hypertension, edema, heart failure, ...

Diuretics are often used in the treatment of hypertension because diuretics have the effect of reducing salt and water, so reducing the volume of fluid should reduce pressure on the artery walls, which has the effect of reducing blood pressure. In addition, some drugs such as chlorthalidone, indapamide also have a vasodilator effect, causing a direct decrease in blood pressure.

Some common side effects of diuretics that patients should note when using them are as follows:
Fluid and electrolyte disturbances: Because diuretics increase sodium salt reabsorption and through transport channels Na-potassium-Cl causes changes in the excretion or reabsorption of ions in body fluids. Loop diuretics (furosemide) reduce sodium, potassium, magnesium, and calcium in the blood, while thiazide diuretics (chlorothiazide, hydrochlorothiazide), thiazide-like (indapamide, chlorthalidone) increase blood calcium and reduce other ions, beneficial Aldosterone-resistant diuretics (spironolactone, amiloride) cause hyperkalemia. Severe disorders can lead to muscle weakness, numbness in the limbs, heart rhythm disturbances, etc. if not detected and treated promptly. The use of high-dose and long-term loop diuretics causes hypocalcemia and also increases urinary calcium, which can cause kidney stones. Acid-base balance disorders: Similarly, Na reabsorption leads to changes in excretion and reabsorption of H+, HCO3-,... ions in body fluids leads to changes in blood pH and disturbances in acid-base balance. The change in blood pH of diuretics is sometimes used in therapy (acetazolamide is used in patients with metabolic alkalosis).

Metabolic disorders: hyperglycemia because of hypokalaemia causes disturbances in glucose tolerance in the periphery and reduces insulin secretion from the pancreas, increases lipids. Hyperuricemia may be observed in patients treated with loop diuretics or thiazide diuretics due to direct or indirect reduction in urate salt excretion. Postural hypotension. In addition, some other side effects of each group such as:
Ototoxicity may cause deafness in some patients infusion of high-dose furosemide diuretics Endocrine side effects causing gynecomastia in men, menstruation abnormality, decreased sex drive of aldosterone-resistant diuretics (amiloride, spironolactone...) In rare cases, side effects may cause dizziness, photosensitivity, and redness of thiazide diuretics.

To limit the side effects of diuretics, patients should:
Use diuretics according to indications, doses and carefully consider when using drugs in patients with diabetes, kidney failure, gout. Diuretics should be taken during the day to avoid nocturia. With long-term use, it is necessary to monitor kidney function, body fluid status (fluid in and out, weight), blood pressure, electrolytes, blood sugar in the first and second week of taking the drug, then after 6 months and 12 months. Be careful of the risk of falling, dizziness, and dizziness due to postural hypotension. Patients taking potassium-lowering diuretics, depending on the case, may be advised to eat potassium-rich foods. Thiazide diuretics may not be effective in patients with a GFR < 30 mL/min and a low effective dose should be used because efficacy is independent of dose, but toxicity increases with dose. If a new or recurrent gout attack occurs, a physician should be consulted to review the use of diuretics.