Diuretics(redirected from osmotic diuretics)
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agents that increase the excretion of urine and decrease the amount of fluid in the tissues and serous cavities. Natriuretics increase the excretion of sodium ions. Diuretics are used primarily to treat edema accompanying cardiovascular, liver, and kidney diseases. Depending on their effect, they are classified as renal diuretics, which act directly on the kidneys and have the most pronounced effect, and extrarenal diuretics, which act indirectly through other systems in the body.
Renal diuretics act by blocking the kidney enzymes responsible for the transport of electrolytes, as well as by inhibiting reabsorption in the terminal tubules, which intensifies the excretion of sodium, chlorine, and potassium ions. Among the renal diuretics are the mercury compounds Mercusal and Novurit and carbonic anhydrase inhibitors such as Diacarb and dichlorphenamide (Daranid)—sulfonamide derivatives that intensify the excretion of bicarbonate, causing a drop in the alkaline reserve in the blood and, in some cases, acidosis. Benzothiadizine and sulfamoylanthranilic and dichlorophenoxyacetic acid derivatives such as dichlothiazide (Hypothiazide), furosemide (Lasix), and ethacrynic acid (Uregit) are extremely potent diuretics that sharply increase the excretion of sodium and have a hypotensive effect. Pyrimidine and pteridine derivatives, such as Allacyl and triamterene (pterofen), inhibit tubular reabsorption of sodium and chlorine ions but do not affect the excretion of potassium. Aldosterone antagonists, including spironolactone (Aldactone and Verospiron), increase the excretion of sodium and decrease the excretion of potassium and urea.
Depending on how they act, extrarenal diuretics are classified as osmotic and other types of agents. Among the osmotic agents are potassium acetate, mannitol, and urea, which are excreted by the kidneys and absorb water. They cause the excretion of sodium and chlorine in proportion to the increase in volume of urine and are used to lower intracranial pressure and reduce cerebral edema. Acid-forming diuretics include ammonium chloride and potassium chloride, which act by the transformation of cations. The ammonium ion is transformed into urea in the liver, the calcium ion settles in the intestine in the form of phosphate or carbonate, and chlorine ions occur in excess in the blood plasma and are excreted by the kidneys with sodium.
Extracts and tinctures are sometimes prepared for use as diuretics from bearberry leaf (tincture or decoction), field horsetail (decoction or fluid extract), and Orthosiphon leaf (tincture).