Isosorbide, diuretic effects

Polyols, such as mannitol, sorbitol, and isosorbide, provide this effect. Sugars, such as glucose and sucrose, also can have a diuretic effect by this mechanism. Although not a polyol, urea has a similar osmotic effect and has been used in the past as an osmotic diuretic. 

Isosorbide is basically a bicyclic form of sorbitol that is used orally to cause a reduction in intraocular pressure in glaucoma cases. Although a diuretic effect is noted, its ophthalmologic properties are its primary value. 

Isosorbide is a diuretic the dinitrate is a vasodilator. Hexahydrofuro[3,2-6 ]pyrrole derivatives are useful as bronchodilators and thrombocyte aggregation inhibitors. 3-Amino-4//-pyrrolo[3,4-c]isoxazoles produce hypotension. 3,4,5,6-Tetrahydro-2H-cycIopen-tathiazol-2-one is an effective analgesic. 

Compared with placebo, the combination of hydralazine and isosorbide dinitrate (ISDN) reduced mortality in patients receiving diuretics and digoxin (but not ACE inhibitors or /3-blockers). However, another trial comparing the combination with an ACE inhibitor found that mortality was lower in the ACE inhibitor group. Adverse effects (primarily headache and gastrointestinal complaints) with combined hydralazine-ISDN were common, limiting their use in many patients. Patient compliance also was an important issue because hydralazine-ISDN therapy was given four times daily in these trials. Whether less frequent administration provides equivalent benefit is unknown. 

Osmotic diuretics are used cautiously in patients with renal or kidney imi>airment or electrolyte imbalance. The osmotic diuretics are Rregnancy Cat iy B (isosorbide) and C (glycerin, mannitol, and urea) dru and must be used cautiously during pr iancy and lactation. Additive hypotensive effects occur when the osmotic diuretics are given witli otlier antihyiiertensive drugs or nitrate. 

Prototypes and Mechanism of Action Mannitol, the prototypical osmotic diuretic, is given intravenously. Other drugs often classified with mannitol (but rarely used) include glycerin, isosorbide, and urea. Because it is freely filtered at the glomerulus but poorly reabsorbed from the tubule, mannitol remains in the lumen and holds water by virtue of its osmotic effect. The major location for this action is the proximal convoluted mbule, where the bulk of isosmotic reabsorption normally takes place. Reabsorption of water is also reduced in the descending limb of the loop of Henle and the collecting tubule. 

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