Loop diuretics hypokalemia with

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. 

The answer is b. (Katzung, pp 256-258J Amiloride is a K-sparing diuretic with a mild diuretic and natriuretic effect The parent compound is active, and the drug is excreted unchanged in the urine. Amiloride has a 24-hour duration of action and is usually administered with a thiazide or loop diuretic (e.g., furosemide) to prevent hypokalemia. The site of its... 

The answer is c. (Hardman, pp 704-706J Triamterene produces retention of the K ion by inhibiting in the collecting duct the reabsorption of Na, which is accompanied by the excretion of K ions. The loop diuretics furosemide and bumetanide cause as a possible adverse action the development of hypokalemia. In addition, thiazides (e g, hydrochlorothiazide) and the thiazide-related agents (e.g., metolazone) can cause the loss of K ions with the consequences of hypokalemia. Triamterene can be given with a loop diuretic or thiazide to prevent or correct the condition of hypokalemia. 

Diuretics - Generally initiate therapy with a thiazide or other oral diuretic. Thiazide-type diuretics are drugs of choice hydrochlorothiazide or chlorthalidone are generally preferred. Reserve loop diuretics for selected patients. This therapy alone may control many cases of mild hypertension. Consider treating diuretic-induced hypokalemia (less than 3.5 mEq/L) with potassium supplementation or by adding a potassium-sparing diuretic to therapy. 

Adjunctive treatment with thiazide or loop diuretics in CHF or hypertension to Help restore normal serum potassium in patients who develop hypokalemia on the kaliuretic diuretic prevent hypokalemia in patients who would be at particular risk if hypokalemia were to develop (eg, digitalized patients or patients with significant cardiac arrhythmias). 

The potassium sparing diuretics are predominantly used in conjunction with thiazides or loop diuretics, with the aim to counteract the hypokalemia induced by the aforementioned types of diuretics. Enhanced natriuresis caused by thiazides or loop diuretics will lead to the following therapeutic benefits. 

Fluid overload occurs commonly in patients with renal failure, often in the absence of associated heart disease. If salt and water intake is not controlled in the patient who is oliguric or anaemic, plasma volume and symptoms of congestive heart failure ensue. Hypertension and coronary heart disease with increasing age contributes to the congestive heart failure. Diuretics like loop-diuretics or metolazone may be of value. Digitalis should be used with caution in patients on dialysis as cardiac arrhythmias may ensue in patients receiving dialysis in the presence of hypokalemia. 

These K+-sparing diuretics have low efficacy when used alone, since only a small amount of total Na+ reabsorption occurs at more distal sites of the nephron. These compounds are used primarily in combination with other diuretics, such as the thiazides and loop diuretics, to prevent or correct hypokalemia. The availability of feed-dose mixtures of thiazides with nonsteroidal K+-sparing compounds has proved a rational form of drug therapy. Both triamterene and amiloride are available alone or in combination with hydrochlorothiazide. 

Therapy with hydrochlorothiazide, up to 50 mg twice daily, or chlorthalidone, 50-100 mg daily, is recommended. Loop diuretics such as furosemide and ethacrynic acid should not be used because they increase urinary calcium excretion. The major toxicity of thiazide diuretics, besides hypokalemia, hypomagnesemia, and hyperglycemia, is hypercalcemia. This is seldom more than a biochemical observation unless the patient has a disease such as hyperparathyroidism in which bone turnover is accelerated. Accordingly, one should screen patients for such disorders before starting thiazide therapy and monitor serum and urine calcium when therapy has begun. 

Alterations in the serum potassium level are hazardous because they can result in cardiac arrhythmias. Drugs that may cause hyperkalemia despite normal renal function include potassium itself, 13 blockers, digitalis glycosides, potassiumsparing diuretics, and fluoride. Drugs associated with hypokalemia include barium, 13 agonists, caffeine, theophylline, and thiazide and loop diuretics. 

The most serious side effects of diuretics are fluid depletion and electrolyte imbalance.13,88 By the very nature of their action, diuretics decrease extracellular fluid volume as well as produce sodium depletion (hyponatremia) and potassium depletion (hypokalemia). Hypokalemia is a particular problem with the thiazide and loop diuretics, but occurs less frequently when the potassium-sparing agents are used. Hypokalemia and other disturbances in fluid and electrolyte balance can produce serious metabolic and cardiac problems and may even prove fatal in some individuals. Consequently, patients must be monitored closely, and the drug dosage should be maintained at the lowest effective dose. Also, potassium supplements are used in some patients to prevent hypokalemia. 

Hypokalemia eventually develops in many patients who are placed on loop diuretics or thiazides. This can often be managed with dietary NaCl restriction. When hypokalemia cannot be managed in this way, or with dietary KC1 supplements, the addition of a potassium-sparing diuretic can significantly lower potassium excretion. While this approach is generally safe, it should be avoided in patients with renal insufficiency in whom life-threatening hyperkalemia can develop in response to potassium-sparing diuretics. 

Fixed combinations of thiazides and loop diuretics with potassium and of thiazides with beta-blockers serve little useful purpose and can in fact do harm. Combinations of thiazides and loop diuretics with potassium-sparing diuretics serve the needs of the small minority of patients who develop clinically significant hypokalemia when given diuretics alone, or in whom hypokalemia is particularly risky. In fact, these combinations are much too widely used, and since individual needs vary so much there is a spectrum of risk, ranging from hypokalemia to hyperkalemia (SEDA-10, 370) (SEDA-10, 371). 

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