CHAPTER 25 Diuretic Agents

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CHAPTER 25 Diuretic Agents. Diuretic Agents. Drugs that accelerate the rate of urine formation Result: removal of sodium and water. Sodium. Where sodium goes, water follows 20% to 25% of all sodium is reabsorbed into the bloodstream in the loop of Henle 5% to 10% in the distal tubules
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CHAPTER 25Diuretic AgentsMosby items and derived items © 2005, 2002 by Mosby, Inc. Diuretic Agents
  • Drugs that accelerate the rate of urine formation
  • Result: removal of sodium and water
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Sodium
  • Where sodium goes, water follows
  • 20% to 25% of all sodium is reabsorbed into the bloodstream in the loop of Henle
  • 5% to 10% in the distal tubules
  • 3% in collecting ducts
  • If water is not absorbed, it is excreted as urine
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Figure 25-1 The nephron and diuretic sites of action. ADH, Antidiuretic hormone.Mosby items and derived items © 2005, 2002 by Mosby, Inc. Diuretic Agents
  • Carbonic anhydrase inhibitors
  • Loop diuretics
  • Osmotic diuretics
  • Potassium-sparing diuretics
  • Thiazide and thiazide-like diuretics
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Carbonic Anhydrase Inhibitors (CAIs)
  • acetazolamide (Diamox)
  • methazolamide
  • dichlorphenamide
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Carbonic Anhydrase Inhibitors: Mechanism of Action
  • The enzyme carbonic anhydrase helps to make H+ ions available for exchange with sodium and water in the proximal tubules
  • CAIs block the action of carbonic anhydrase, thus preventing the exchange of H+ ions with sodium and water
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Carbonic Anhydrase Inhibitors: Mechanism of Action (cont'd)
  • Inhibition of carbonic anhydrase reduces H+ ion concentration in renal tubules
  • As a result, there is increased excretion of bicarbonate, sodium, water, and potassium
  • Resorption of water is decreased and urine volume is increased
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Carbonic Anhydrase Inhibitors: Indications
  • Adjunct agents in the long-term management of open-angle glaucoma
  • Used with miotics to lower intraocular pressure before ocular surgery in certain cases
  • Also useful in the treatment of:
  • Glaucoma
  • Edema
  • Epilepsy
  • High-altitude sickness
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Carbonic Anhydrase Inhibitors: Indications (cont'd)
  • Acetazolamide is used in the management of edema secondary to HF when other diuretics are not effective
  • CAIs are less potent diuretics than loop diuretics or thiazides—the metabolic acidosis they induce reduces their diuretic effect in 2 to 4 days
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Metabolic acidosisAnorexiaHematuriaPhotosensitivityIn diabetic patients: can elevate blood glucose level DrowsinessParesthesiasUrticariaMelenaCarbonic Anhydrase Inhibitors: Side EffectsMosby items and derived items © 2005, 2002 by Mosby, Inc. Loop Diuretics
  • bumetanide (Bumex)
  • ethacrynic acid (Edecrin)
  • furosemide (Lasix)
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Loop Diuretics: Mechanism of Action
  • Act directly on the ascending limb of the loop of Henle to inhibit sodium and chloride resorption
  • Increase renal prostaglandins, resulting in the dilation of blood vessels and reduced peripheral vascular resistance
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Loop Diuretics: Drug Effects
  • Potent diuresis and subsequent loss of fluid
  • Decreased fluid volume causes:
  • Reduced BP
  • Reduced pulmonary vascular resistance
  • Reduced systemic vascular resistance
  • Reduced central venous pressure
  • Reduced left ventricular end-diastolic pressure
  • Potassium depletion
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Loop Diuretics:Indications
  • Edema associated with HF or hepatic or renal disease
  • Control of hypertension
  • Increase renal excretion of calcium in patients with hypercalcemia
  • Useful when rapid diuresis is desired because of rapid onset of action
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Loop Diuretics: Side EffectsBody SystemEffectCNS Dizziness, headache, tinnitus, blurred visionGI Nausea, vomiting, diarrheaMosby items and derived items © 2005, 2002 by Mosby, Inc. Loop Diuretics: Side Effects (cont'd)Body SystemEffectHematologic Agranulocytosis, neutropenia, thrombocytopeniaMetabolic Hypokalemia, hyperglycemia, hyperuricemiaMosby items and derived items © 2005, 2002 by Mosby, Inc. Osmotic Diuretics
  • mannitol (Osmitrol)
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Osmotic Diuretics: Mechanism of Action
  • Work in the proximal tubule
  • Nonabsorbable, producing an osmotic effect
  • Pull water into the blood vessels and nephrons from the surrounding tissues
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Osmotic Diuretics: Drug Effects
  • Reduced cellular edema
  • Increased urine production, causing diuresis
  • Rapid excretion of water, sodium, and other electrolytes, as well as excretion of toxic substances from the kidney
  • Reduced excessive intraocular pressure
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Osmotic Diuretics: Indications
  • Used in the treatment of patients in the early, oliguric phase of ARF
  • To promote the excretion of toxic substances
  • Reduction of intracranial pressure
  • Treatment of cerebral edema
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Osmotic Diuretics: Side Effects
  • Convulsions
  • Thrombophlebitis
  • Pulmonary congestion
  • Also headaches, chest pains, tachycardia, blurred vision, chills, and fever
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Potassium-Sparing Diuretics
  • amiloride (Midamor)
  • spironolactone (Aldactone)
  • triamterene (Dyrenium)
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Potassium-Sparing Diuretics: Mechanism of Action
  • Work in collecting ducts and distal convoluted tubules
  • Interfere with sodium-potassium exchange
  • Competitively bind to aldosterone receptors
  • Block the resorption of sodium and water usually induced by aldosterone
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Potassium-Sparing Diuretics: Drug Effects
  • Prevent potassium from being pumped into the tubule, thus preventing its secretion
  • Competitively block the aldosterone receptors and inhibit its action
  • The excretion of sodium and water is promoted
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Potassium-Sparing Diuretics: Indications
  • spironolactone and triamterene
  • Hyperaldosteronism
  • Hypertension
  • Reversing the potassium loss caused by potassium-losing drugs
  • amiloride
  • Treatment of HF
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Potassium-Sparing Diuretics: Side EffectsBody SystemEffectCNS Dizziness, headacheGI Cramps, nausea, vomiting, diarrheaOther Urinary frequency, weakness **hyperkalemia**Mosby items and derived items © 2005, 2002 by Mosby, Inc. Potassium-Sparing Diuretics: Side Effects (cont'd)spironolactone
  • Gynecomastia
  • Amenorrhea
  • Irregular menses
  • Postmenopausal bleeding
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Thiazide and Thiazide-like Diuretics
  • Thiazide diuretics
  • hydrochlorothiazide (Esidrix, HydroDIURIL)
  • chlorothiazide (Diuril)
  • trichlormethiazide (Metahydrin)
  • Thiazide-like diuretics
  • chlorthalidone (Hygroton)
  • metolazone (Mykrox, Zaroxolyn)
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Thiazide and Thiazide-like Diuretics: Mechanism of Action
  • Inhibit tubular resorption of sodium and chloride ions
  • Action primarily in the ascending loop of Henle and early distal tubule
  • Result: water, sodium, and chloride are excreted
  • Potassium is also excreted to a lesser extent
  • Dilate the arterioles by direct relaxation
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Thiazide and Thiazide-like Diuretics: Drug Effects
  • Lowered peripheral vascular resistance
  • Depletion of sodium and water
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Thiazide and Thiazide-like Diuretics: Indications
  • Hypertension (one of the most prescribed group of agents for this)
  • Edematous states
  • Idiopathic hypercalciuria
  • Diabetes insipidus
  • Adjunct agents in treatment of HF, hepatic cirrhosis
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Thiazide and Thiazide-like Diuretics: Side EffectsBody SystemEffectCNS Dizziness, headache, blurred vision, paresthesias, decreased libidoGI Anorexia, nausea, vomiting, diarrheaMosby items and derived items © 2005, 2002 by Mosby, Inc. Thiazide and Thiazide-like Diuretics: Side Effects (cont'd)Body SystemEffectGU ImpotenceIntegumentary Urticaria, photosensitivityMetabolic Hypokalemia, glycosuria, hyperglycemia Mosby items and derived items © 2005, 2002 by Mosby, Inc. Nursing Implications
  • Perform a thorough patient history and physical examination
  • Assess baseline fluid volume status, intake and output, serum electrolyte values, weight, and vital signs—especially postural BPs
  • Assess for disorders that may contraindicate or necessitate cautious use of these agents
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Nursing Implications
  • Instruct patients to take in the morning as much as possible to avoid interference with sleep patterns
  • Monitor serum potassium levels during therapy
  • Potassium supplements are usually not recommended when potassium levels exceed 3 mEq/L
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Nursing Implications
  • Teach patients to maintain proper nutritional and fluid volume status
  • Teach patients to eat more potassium-rich foods when taking any but the potassium-sparing agents
  • Foods high in potassium include bananas, oranges, dates, raisins, plums, fresh vegetables, potatoes, meat, and fish
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Nursing Implications
  • Patients taking diuretics along with a digitalis preparation should be taught to monitor for digitalis toxicity, which may happen in the presence of hypokalemia (Hydrochlorothiazide is one example)
  • Diabetic patients who are taking thiazide and/or loop diuretics should be told to monitor blood glucose and watch for elevated levels
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Nursing Implications
  • Teach patients to change positions slowly, and to rise slowly after sitting or lying to prevent dizziness and possible fainting related to orthostatic hypotension
  • Encourage patients to keep a log of their daily weight
  • Encourage patients to return for follow-up visits and labwork
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Nursing Implications
  • Patients who have been ill with nausea, vomiting, and/or diarrhea should notify their physician because fluid loss may be dangerous
  • Signs and symptoms of hypokalemia include muscle weakness, constipation, irregular pulse rate, and overall feeling of lethargy
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Nursing Implications
  • Instruct patients to notify the physician immediately if they experience rapid heart rates or syncope (reflects hypotension or fluid loss)
  • A weight gain of 2 or more pounds a day or 5 or more pounds a week should be reported immediately
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Nursing ImplicationsExcessive consumption of licorice can lead to an additive hypokalemia in patients taking thiazidesMosby items and derived items © 2005, 2002 by Mosby, Inc. Nursing ImplicationsMonitor for adverse effects
  • Metabolic alkalosis, drowsiness, lethargy, hypokalemia, tachycardia, hypotension, leg cramps, restlessness, decreased mental alertness
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc. Nursing Implications
  • Monitor for therapeutic effects
  • Reduction in edema, fluid volume overload, HF
  • Reduction of hypertension
  • Return to normal intraocular pressures
  • Mosby items and derived items © 2005, 2002 by Mosby, Inc.
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