Diuretic
| Classification of common diuretics and their mechanisms of action |
| agent | mechanism |
| Potassium-sparing diuretics (e.g., spironolactone, amiloride, triamterene) | inhibition within collecting ducts of Na+-K+ exchange: spironolactone inhibits aldosterone action; amiloride inhibits epithelial sodium channels (ENaC) |
| water | inhibits vasopressin secretion |
| ethanol | inhibits vasopressin secretion |
| V2 vasopressin receptor antagonists | inhibit vasopressin's action on nephron's collecting duct |
| Xanthines (e.g., caffeine, theophylline) | inhibit tubular reabsorption of Na+, increase glomerular filtration rate| acidifying salts (e.g., CaCl2, NH4Cl) | | | carbonic anhydrase inhibitors (e.g., acetazolamide, dorzolamide) | inhibit H+ secretion, resultant promotion of Na+ and K+ excretion | | loop diuretics (e.g., furosemide, bumetanide, ethacrynic acid) | inhibit the cotransporter in the medullary thick ascending limb of the loop of Henle | | Thiazides (e.g., hydrochlorothiazide, bendroflumethiazide) | inhibit Na+/Cl- reabsorption from the distal convoluted tubules of nephrons | | Osmotic diuretics (e.g., mannitol, glucose) | promote osmotic diuresis | |
A
diuretic (colloquially called a water pill) is any
drug that elevates the rate of bodily
urine excretion (
diuresis). Diuretics also decrease the
extracellular fluid (ECF) volume, and are primarily used to produce a negative extracellular fluid balance.
Caffeine,
cranberry juice and
alcohol are all weak diuretics.
In
medicine, diuretics are used to treat
heart failure,
liver cirrhosis,
hypertension and certain
kidney diseases. Diuretics alleviate the symptoms of these diseases by causing
sodium and
water loss through the urine. As urine is produced by the
kidney, sodium and water – which cause
edema related to the disease – move into the
blood to replace the volume lost as urine, thereby reducing the pathological edema. Some diuretics, such as
acetazolamide, help to make the
urine more
alkaline and are helpful in increasing excretion of substances such as
aspirin in cases of
overdose or poisoning.
The antihypertensive actions of some diuretics (
thiazides and
loop diuretics in particular) are independent of their diuretic effect. That is, the reduction in blood pressure is not due to decreased blood volume resulting from increased urine production, but occurs through other mechanisms and at lower doses than that required to produce diuresis.
Indapamide was specifically designed with this is mind, and has a larger therapeutic window for hypertension (without pronounced diuresis) than most other diuretics.
Chemically, diuretics are a diverse group of compounds that either stimulate or inhibit various
hormones that naturally occur in the body to regulate urine production by the kidneys.
Alcohol produces diuresis through modulation of the
vasopressin system.
