Diuretics, loop

Diuretics are needed to return to normal the expanded extracellular volume that other antihypertensive agents produce, such as fluid retention and blood volume expansion, via compensatory mechanisms of the body. The loss of efficacy of antihypertensive agents can be restored if a diuretic is used concomitandy. In the treatment of hypertension, high ceiling or loop diuretics, such as furosemide, ethacrynic acid, and bumetanide, are no more efficacious than the thiazide-type of diuretics. In fact, these agents cause more side effects, such as dehydration, metaboHc alkalosis, etc, and therefore, should not be used except in situations where rapid elimination of duid volume is cleady indicated. 

Potassium Sparing Diuretics. Triamterene and amiloride, potassium sparing diuretics, by themselves produce only slight antihypertensive effects. The main use is to prevent or to treat the hypokalemia induced by thiazide-type and high ceiling loop diuretics, such as furosemide and bumetanide. 

Ascites. Patients with cirrhosis, especially fiver cirrhosis, very often develop ascites, ie, accumulation of fluid in the peritoneal cavity. This is the final event resulting from the hemodynamic disturbances in the systemic and splanchnic circulations that lead to sodium and water retention. When therapy with a low sodium diet fails, the dmg of choice for the treatment of ascites is furosemide, a high ceiling (loop) diuretic, or spironolactone, an aldosterone receptor antagonist/potassium-sparing diuretic. 

Agents acting in the proximal tubule are seldom used to treat hypertension. Treatment is usually initiated with a thiazide-type diuretic. Chlorthalidone and indapamide are structurally different from thiazides but are functionally related. If renal function is severely impaired (i.e., serum creatinine above 2.5 mg/dl), a loop diuretic is needed. A potassium-sparing agent may be given with the diuretic to reduce the likelihood of hypokalemia. 

The use of CA inhibitors as diuretics is limited by their propensity to cause metabolic acidosis and hypokalemia. Their use can be indicated in patients with metabolic alkalosis and secondary hyperaldosteronism resulting for example from aggressive use of loop diuretics. Furthermore, CA inhibitors are effective dtugs to produce a relatively alkaline urine for the treatment of cysteine and uric acid stones as well as for the accelerated excretion of salicylates. Perhaps the most common use of CA inhibitors is in the treatment of glaucoma. 

Loop diuretics are the drugs of choice for the treatment of edematous patients with congestive heart failure, cirrhosis of the liver, and nephrotic syndrome. Excretion of Na is helpful only to the extent that some of the... 

NKCC is a heavily glycosylated protein with 12 putative membrane-spanning regions. Thirty percent of the sodium that is filtered by renal glomeruli is reabsorbed by Na-K-2C1 cotransport in the ascending limb of Henle in the nephron. Na-K-2C1 cotransport is a target of all loop diuretics. 

Locus Cemleus Long-Chain Fatty Acids Long-QT Syndromes Long-Term Depression Long-Term Potentiation Loop Diuretics... 

Administration of the aminoglycosides with the cephalosporins may increase the risks of nephrotoxicity. When the aminoglycosides are administered with loop diuretics there is an increased risk of ototoxicity (irreversible hearing loss). There is an increased risk of neuromuscular blockage (paralysis of the respiratory muscles) if the aminoglycosides are given shortly after general anesthetics (neuromuscular junction blockers). 

Acetaminophen may alter blood glucose test results, causing falsely lower blood glucose values. Use with the barbiturates, hydantoins, isoniazid, and rifampin may increase the toxic effects and possibly decrease the therapeutic effects of acetaminophen. The effects of the loop diuretics may be decreased when administered with acetaminophen. Hepatotoxicity has occurred in chronic alcoholics who are taking moderate doses of acetaminophen. 

Fhtients taking a diuretic and a digitalis glycoside must be monitored closely. Thiazide and loop diuretics (see Chap. 46) may increase the risk and effects of toxicity. 

The effects of warfarin may increase when administered with acetaminophen, NSAIDs, beta blockers, disulfiram, isoniazid, chloral hydrate, loop diuretics, aminoglycosides, cimetidine, tetracyclines, and cephalosporins. Oral contraceptives, ascorbic acid, barbiturates, diuretics, and vitamin K decrease the effects of warfarin. Because die effects of warfarin are influenced by many drugp, die patient must notify die nurse or die primary healdi care provider when taking a new drug or discontinuing... 

Diuretics are used in a variety of medical disorders. The primary health care provider selects the type of diuretic diat will most likely be effective for treatment of a specific disorder. In some instances, hypertension may be treated with the administration of an antihypertensive drug and a diuretic. The diuretics used for this combination tiierapy include the loop diuretics and the thiazides and related diuretics. The specific uses of each type of diuretic drug are discussed in the following sections. 

Figure 46-1. The nephron is the functional unit of the kidney. Note the various tubules, the site of most diuretic activity. The loop of Henle is the site of action for the loop diuretics. Thiazide diuretics ad at the ascending portion of the loop of Henle and the distal tube of the nephron.

The loop diuretics, furosemide (Lasix) and ethacrynic acid (Edecrin), increase the excretion of sodium and chloride by inhibiting reabsorption of these ions in the... 

Loop diuretics are used in the treatment of edema associated with CHF, cirrhosis of the liver, and renal disease, including the nephrotic syndrome. These drug s are particularly useful when a greater diuretic effect is desired. Furosemide is the drug of choice when a rapid diuresis is needed or if the patient has renal insufficiency. Furosemide and torsemide are also used to treat hypertension. Ethacrynic acid is also used for the short-term management of ascites caused by a malignancy, idiopathic edema, or lymphedema. 

Loop diuretics are contraindicated in patients with known hypersensitivity to the loop diuretics or to the sulfonamides, severe electrolyte imbalances, hepatic coma, or anuria, and in infants (ethacrynic acid). 

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