Diuretics: Chemical | Organic composition
Last modified: Sunday, 31. May 2009 - 1:51 pm
Diuretics work by increasing the amount of sodium and fluids excreted by the kidneys. Less fluid means less total blood volume and improved circulation and blood pressure. There are five main classes of the drug: loop diuretics, thiazide diuretics, potassium-sparing diuretics, osmotic diuretics, and carbonic anhydrase inhibitors.
The most potent type of diuretic, loop diuretics are named after the loop of Henle, a component of a nephron. The nephrons are the filtering units of the kidney, and are responsible for moving fluids and waste out of the bloodstream, resulting in urine formation. The loop of Henle is a branch within each nephron where sodium and potassium are reabsorbed back into the bloodstream instead of being filtered into the urine. Loop diuretics inhibit this action and promote excretion of the sodium and potassium instead, along with calcium and magnesium. Since excess sodium causes excess fluid build-up, this results in fluid loss. Furosemide (Lasix), bumetanide (Bumex), torsemide (Demadex), and ethacryinic acid (Edecrin) are all loop diuretics.
Thiazide diuretics such as chlorothiazide (Diuril) and hydrochlorothiazide (HCTZ) work by blocking the action of aldosterone, a hormone that promotes sodium reabsorption by the kidneys. They are potassium-depleting diuretics, meaning that they cause a loss of potassium, known as hypokalemia.
Potassium-sparing diuretics include amiloride (Midamor) and triamterene (Dyrenium). They are used in the treatment of cirrhosis and congestive heart failure. They may be used in conjunction with thiazide diuretics to offset the potassium loss associated with those medications.
As their name suggests, osmotic diuretics such as mannitol (Osmitrol), isosorbide (Ismotic), and glycerin (Osmoglyn) draw fluid from the tissues of the body through principles of osmosis. Osmotic diuretics are typically given to treat or prevent acute renal failure (kidney failure). They may also be used to relieve intracranial pressure (swelling of the brain) in cases of head injury or hydrocephalus.
Carbonic anhydrase inhibitors
Carbonic anhydrase inhibitors such as dorzolamide (Trusopt) and dichlorphenamide (Daranide) are used to treat glaucoma patients and altitude sickness. Acetazolamide (Diamox), a carbonic anhydrase inhibitor, is also used to treat seizures related to epilepsy. CA inhibitors work by promoting the excretion of sodium and bicarbonate.