Loop diuretics
The loop diuretics, also called high ceiling diuretics because they induce an extremely important diuresis, are furosemide (Lasix*), bumetanide (Burinex*), piretanide (Arelix*) and torsemide also called torasemide (Demadex*).
Secreted in the lumen of the proximal tubule, they act at the level of the broad part of the ascending limb of Henle's loop where they inhibit the cotransport of symport type Na+/ K+-2Cl- by probably binding to the chloride site of the cotransporter. Thus, they decrease the reabsorption of sodium, potassium and chloride whose urinary elimination increases.
They also increase the urinary elimination of calcium and magnesium.
At the glomerular level, they could improve the blood flow rate and increase filtration, effects which could be suppressed by antagonists of prostaglandins like indomethacine.
Loop diuretics have an action with an extremely fast onset, of short duration - lower than six hours after administration by oral route, and lower than two hours after parenteral administration - very intense, being able to reach the elimination of 25% of the glomerular filtrate.
They are indicated as standard formulation (not sustained release), taking into account the intensity and of the speed of their effect, in the treatment of the congestive heart failure, in particular acute pulmonary edema.
The preparations with progressive and sustained release of the active ingredient have less intense effects and longer duration of action. They can be used for the treatment of arterial hypertension. ;
Their adverse effects are rather similar to those of thiazide diuretics, with however a greater risk of hyponatremia and dehydration.
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