Diuretic agents osmotic

Modern diuretics (natriuretics, saluretics), as used in the treatment of hypertension and heart failure, are administered with the aim to enhance the renal excretion of sodium ions and water. Older diuretics, such as the osmotic diuretic agents, are of little interest in the treatment of the aforementioned cardiovascular disorders, but may be used to lower intracranial pressure associated with brain edema. 

Many diuretic agents (loop diuretics, thiazides, amiloride, and triamterene) exert their effects on specific membrane transport proteins in renal tubular epithelial cells. Other diuretics exert osmotic effects that prevent water reabsorption (mannitol), inhibit enzymes (acetazolamide), or interfere with hormone receptors in renal epithelial cells (spironolactone). 

Osmotically acting diuretic agents. These are applied in the treatment of intoxication in order to increase the urine volume and accelerate elimination of the poison ( forced diuresis ). The classical example is mannitol. This sugar is quite similar to glucose in structure but does not get metabolized nor reabsorbed from the primary glomerular filtrate in the kidneys. 

Dimethyl sulfoxide (DMSO) has also been suggested as a potent osmotic diuretic in horses. However, one study that compared the diuretic effects of DMSO with furosemide (frusemide, Img/kg) and hypertonic saline (5 liters) found that DMSO (Ig/kg administered i.v. diluted in 5 liters of 0.9% sodium chloride) was a relatively weak diuretic agent that doubled 4-h urine production in comparison with that achieved with the same volume of isotonic (0.9%) sodium chloride. The most dramatic diuretic response was produced by the hypertonic saline (7.5%), which resulted in the production of more than 40 ml/kg urine during the first 4-h period after administration (Schott Black 1995). 

Malignant neoplasms Fanconi s syndrome Acute volume expansion Metabolic acidosis Renal transplantation Vitamin D deficiency and/or resistance Diuretics Acetazolamide Osmotic agents Glucocorticoids Sodium bicarbonate Internal redistribution Refeeding syndrome Parenteral nutrition... 

Manufacture of vitamin C starts with the conversion of sorbitol to L-sorbose. Sorbitol and xyHtol have been used for parenteral nutrition following severe injury, bums, or surgery (246). An iron—sorbitol—citric acid complex is an intramuscular bematinic (247). Mannitol administered intravenously (248) and isosorbide administered orally (249) are osmotic diuretics. Mannitol hexanitrate and isosorbide dinitrate are antianginal dmgs (see Cardiovascular agents). 

Osmotherapy employs agents such as mannitol, glycerol, and hypertonic saline to create an osmotic gradient between the brain (optimally, the edematous infarcted tissue) and the bloodstream, such that water is drawn out from the brain, thereby reducing edema. Each of these agents has been shown to be effective, and may be used alone or in combination with a diuretic, such as furosemide. Their action, however, depends upon an intact blood-brain barrier (BBB), and concerns have been raised for possible paradoxical worsening when one is absent. In this hypothesis, mannitol extravasates from the vessel into the interstitial tissue and water follows a new osmotic... 

Mannitol is an agent that may be used in patients with I impending cerebral herniation. Mannitol is an osmotic diuretic that shifts brain osmolarity from the brain to the blood. Doses of 100 g (1-2 g/kg) as an intravenous bolus should be used. Repeated doses typically are not recommended because mannitol may diffuse into damaged brain tissue, leading to rebound increased ICP.21... 

Diuretics are a group of therapeutic agents designed to reduce the volume of body fluids. Their mechanism of action is at the level of the kidney and involves an increase in the excretion of Na+ and Cl ions and, consequently, an increase in urine production. As discussed in Chapter 2, sodium is the predominant extracellular cation and, due to its osmotic effects, a primary determinant of extracellular fluid volume. Therefore, if more sodium is excreted in the urine, then more water is also lost, thus reducing the volume of extracellular fluids including the plasma. 

Forced diuresis is occasionally useful. It may cause volume overload or electrolyte disturbances. Forced diuresis is useful for phenobarbital, bromides, lithium, salicylate, or amphetamines overdoses. Do not use for tricyclic antidepressants, sedative-hypnotics, or highly protein-bound medications. The most common agents employed are furosemide and osmotic diuretics with mannitol. 

Ideally, the distribution of osmotic diuretics should be largely confined to the vascular system, although this can lead to excessive expansion of the vascular compartment. Such an overexpansion could precipitate pulmonary edema or increase cardiac work or both. This is largely the result of rapid transfer of fluid from the interstitial to the vascular compartment. Practically speaking, however, few osmotic diuretics are available for therapeutic use. These agents, therefore, should be given cautiously to patients with compromised cardiac function. 

Mechanism of Action An osmotic diuretic, antiglaucoma, and antihemolytic agent that elevates osmotic pressure of theglomerular filtrate, inhibiting tubular reabsorption of water and electrolytes, resulting in increased flow of water into interstitial fluid and plasma. Therapeutic Effect Produces diuresis reduces lOP reduces iCP and cerebral edema. 

Other drugs, such as verapamil, caffeine, theophylline, osmotic diuretics, carbonic anhydrase inhibitors, or aminophylline, can increase lithium excretion, possibly dropping plasma levels below the therapeutic threshold ( 329). Further, if doses are increased to compensate for this effect, care must be taken to readjust the lithium downward when these concomitant agents are reduced or discontinued. 

Technically, a "diuretic" is an agent that increases urine volume, whereas a "natriuretic" causes an increase in renal sodium excretion. Because natriuretics almost always also increase water excretion, they are usually called diuretics. Osmotic diuretics (see under Agents That Alter Water Excretion) are diuretics that are not directly natriuretic. 

Agents That Alter Water Excretion OSMOTIC DIURETICS... 

The proximal tubule and descending limb of Henle s loop are freely permeable to water (Table 15-1). Any osmotically active agent that is filtered by the glomerulus but not reabsorbed causes water to be retained in these segments and promotes a water diuresis. Such agents can be used to reduce intracranial pressure and to promote prompt removal of renal toxins. The prototypic osmotic diuretic is mannitol. 

Osmotic diuretics are used to increase water excretion in preference to sodium excretion. This effect can be useful when avid Na + retention limits the response to conventional agents. It can be used to maintain urine volume and to prevent anuria that might otherwise result from presentation of large pigment loads to the kidney (eg, from hemolysis or rhabdomyolysis). Some oliguric patients do not respond to osmotic diuretics. Therefore, a test dose of mannitol (12.5 g intravenously) should be given before starting... 

The clinical management of brain injury includes the use of osmotic and other diuretics to attempt to control tissue edema and agents which modify the rheology of blood in order to better perfuse the brain and counter ischemia. Two recent reports summarize the effects of hemodilution with DCLHb or oncotically... 

Therapeutically, mannitol administered parenterally is used as an osmotic diuretic, as a diagnostic agent for kidney function, as an adjunct in the treatment of acute renal failure, and as an agent to reduce intracranial pressure, treat cerebral edema, and reduce intraocular pressure. Given orally, mannitol is not absorbed significantly from the GI tract, but in large doses it can cause osmotic diarrhea see Section 14. 

The osmotic diuretics (e.g. mannitol, sucrose, urea and glycerol) are agents that are filtered freely in the glomeruli, reabsorbed poorly in the tubules and pharmacologically inert. As sodium and water are reabsorbed in the proximal tubule and the loop of Henle, the osmotic diuretics are... 

Chemical/Pharmaceutical/Other Class Diuretic, osmotic agent, and dermatological agent... 

Urea is used as an osmotic to treat problems like high pressure in the eye ball (glaucoma). It is also used as a diuretic and as a topical dermatological agent in treating psoriasis, and other dry, scaly conditions. 

DERMATOLOGICAL AGENT in a number of skin preparations, e.g. to treat eczema and psoriasis (as a hydrating agent). It can be given intravenously as a hypertonic dehydrating (osmotic) diuretic to reduce intracranial pressure in controlling cerebral oedema. 

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