Quinethazone (brand name Hydromox) is a thiazide diuretic used to treat hypertension. The antihypertensive mechanism of quinethazone is less well understood. This drug was discovered in a period when only isoform carbonic anhydrases (CAs) II was known and considered physiologically/pharmacologically relevant. Recently was studied that quinethazone considerably inhibit other isozymes known nowadays to be involved in critical physiologic processes. Thiazides like quinethazone also inhibit sodium ion transport across the renal tubular epithelium through binding to the thiazide sensitive sodium-chloride transporter. Common side effects include dizziness, dry mouth, nausea, and low potassium levels. Thiazides may increase the toxicity of allopurinol, anesthetics, antineoplastic, calcium salts, diazoxide, digitalis, lithium; loop diuretics, methyldopa, nondepolarizing muscle relaxants, vitamin D; amphotericin B and anticholinergics may increase the toxicity of thiazides.