Furosemide, bumetanide, torsemide, and
ethacrynic acid are "high-ceiling"
loop diuretics acting primarily at
the ascending limb of the loop of
effectiveness of these agents is related to their
site of action because reabsorption of about 30 -
40% of the filtered sodium and chloride load
occurs at the ascending loop. Distal sites are
not able to compensate completely for this
magnitude of reduction of NaCl reabsorption.
Loop diuretics increase urinary Ca2+
in contrast to the action of thiazides.
Loop diuretics also increase renal blood
flow by decreasing renal vascular resistance.
These drugs are beneficial in managing
systemic and pulmonary fluid overload produced by
congestive heart failure (CHF). By i.v.
administration they are particularly effective in
resolving acute pulmonary edema.