Diuretics are class of drugs which causes net loss of Na+ and water in urine. This class is one of the common prescribed drugs. They are classified according to the efficacy. Loop diuretics prevent re-absorption of sodium and chloride ions in the Loop of Henle by inhibiting Na+-K+-2Cl- cotransporter. Thiazide diuretics inhibit sodium re-absorption at the beginning of the distal convoluted tubules. Potassium sparing diuretics prevent excessive loss of potassium at the distal convoluted tubules.
Osmotic diuretics act as osmotic load and increase the urine output. They are used in raised intracranial pressure. Diuretics in general are used to treat edema, hypertension, heart failure and various other diseases. Loop diuretics are faster acting which provide quick relief in left ventricular failure and pulmonary edema. These are used to relieve edema irrespective of etiology- cardiac, hepatic or renal.
Thiazide diuretics act on Na+-Cl- symport at distal tubule. In addition they reduces renal Ca2+ excretion. They are one of the first line of drug in treatment of hypertension. They act best in edema due to cardiac cause. Both, loop and thiazide diuretics cause hypokalaemia. Potassium sparing diuretics like spironolactone (aldosterone antagonist) are used in combination with thiazide or loop diuretics to counteract hypokalaemia.
