1. Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
Chapter 28
Diuretic Drugs
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2. Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
Diuretic Drugs
Drugs that accelerate the rate of urine formation
Result in the removal of sodium and water
Used in the treatment of hypertension, heart failure, and renal failure
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3. Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
Sodium
In the nephron, where sodium goes, water follows
60% to 70% of sodium and water is returned to bloodstream by the proximal tubule
20% to 25% of all sodium is reabsorbed into the bloodstream in the ascending loop of Henle
5% to 10% is reabsorbed in the distal tubules
3% is reabsorbed in collecting ducts
If water is not absorbed, it is excreted as urine
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4. The Nephron and Diuretic Sites of Action
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5. Classroom Response Question
Which location is the area where the highest percentage of sodium and water are resorbed back into the bloodstream?
Glomerulus
Proximal tubule
Ascending loop of Henle
Distal tubule
Correct answer: B
Rationale: The proximal convoluted (twisted) tubule or, more simply, proximal tubule, anatomically follows the glomerulus and returns 60% to 70% of the sodium and water from the filtered fluid back into the bloodstream. Another 20% to 25% of sodium is resorbed into the bloodstream in the ascending loop of Henle. The remaining 5% to 10% of sodium resorption takes place in the distal convoluted tubule, often called simply the distal tubule, which anatomically follows the ascending loop of Henle. The glomerulus does not resorb sodium or water, but instead is the point of initial filtration of the blood.
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6. Types of Diuretic Drugs
Carbonic anhydrase inhibitors
Loop diuretics
Osmotic diuretics
Potassium-sparing diuretics
Thiazide and thiazide-like diuretics
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7. Carbonic Anhydrase Inhibitors (CAIs)
acetazolamide (Diamox)
Most commonly used CAI
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8. 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
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9. 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
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10. Carbonic Anhydrase Inhibitors: Indications
Adjunct drugs 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:
Edema
High-altitude sickness
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11. Carbonic Anhydrase Inhibitors: Indications (cont’d)
Acetazolamide (Diamox) is used in the management of edema secondary heart failure (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
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12. Carbonic Anhydrase Inhibitors: Adverse Effects
Metabolic acidosis
Anorexia
Hematuria
Photosensitivity
Melena
Hypokalemia
Drowsiness
Paresthesias
Urticaria
Glycosuria in diabetic patients
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Loop Diuretics
bumetanide (Bumex)
ethacrynic acid (Edecrin)
furosemide (Lasix)
torsemide (Demadex)
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14. Loop Diuretics: Mechanism of Action
Possess renal, cardiovascular, and metabolic effects
Act directly on the ascending limb of the loop of Henle to inhibit chloride and sodium resorption
Increase renal prostaglandins, resulting in the dilation of blood vessels and reduced peripheral vascular resistance
Useful in treatment of edema
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15. Loop Diuretics: Drug Effects
Potent diuresis and subsequent loss of fluid
Decreased fluid volume causes a reduction in:
Blood pressure
Pulmonary vascular resistance
Systemic vascular resistance
Central venous pressure
Left ventricular end-diastolic pressure
Potassium and sodium depletion
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16. Loop Diuretics: Indications
Edema associated with HF or hepatic or renal disease
To control hypertension
To increase renal excretion of calcium in patients with hypercalcemia
In cases of HF resulting from diastolic dysfunction
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17. Loop Diuretics: Adverse Effects
Body System Adverse Effects
Central nervous system (CNS) Dizziness, headache, tinnitus, blurred vision
Gastrointestinal (GI) Nausea, vomiting, diarrhea
Integumentary Stevens-Johnson
syndrome (torsemide)
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18. Loop Diuretics: Adverse Effects (cont’d)
Body System Adverse Effects
Hematologic Agranulocytosis, neutropenia, thrombocytopenia
Metabolic Hypokalemia, hyperglycemia, hyperuricemia
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19. Classroom Response Question
When administering a loop diuretic to a patient, it is most important for the nurse to determine if the patient is also taking which drug?
lithium (Eskalith)
acetaminophen (Tylenol)
penicillin
theophylline
Correct answer: A
Rationale: Use of loop diuretics with lithium can increase the risk of lithium toxicity. Drug interactions with loop diuretic therapy can occur with concurrent use of nonsteroidal antiinflammatory drugs (NSAIDs), and vancomycin can cause increased neuro- and ototoxicity when used with loop diuretics. There is no associated risk of drug interaction when taking acetaminophen, penicillin, or theophylline with loop diuretics.
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Osmotic Diuretics
mannitol (Osmitrol)
Most used osmotic diuretic
Urea
Organic acids
Glucose
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21. Osmotic Diuretics: Mechanism of Action
Work mostly in the proximal tubule
Nonabsorbable, producing an osmotic effect
Pull water into the renal tubules from the surrounding tissues
Inhibit tubular resorption of water and solutes, thus producing rapid diuresis
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22. Osmotic Diuretics: Drug Effects
Increases glomerular filtration rate and renal plasma flow—helps to prevent kidney damage during acute renal failure
Reduces intracranial pressure or cerebral edema associated with head trauma
Reduces excessive intraocular pressure
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23. Osmotic Diuretics: Indications
Treatment of patients in the early, oliguric phase of acute renal failure (ARF)
To promote excretion of toxic substances
To reduce intracranial pressure
Treatment of cerebral edema
NOT indicated for peripheral edema
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24. Osmotic Diuretics: Adverse Effects
Convulsions
Thrombophlebitis
Pulmonary congestion
Also headaches, chest pains, tachycardia, blurred vision, chills, and fever
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25. Osmotic Diuretics: Mannitol (Osmitrol)
Intravenous infusion only
May crystallize when exposed to low temperatures
Use of a filter is required
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26. Classroom Response Question
While preparing an infusion of mannitol (Osmitrol), the nurse notices small crystals in the IV tubing. The most appropriate action by the nurse is to
administer the infusion slowly.
discard the solution and obtain another bag of medication.
obtain a filter, and then infuse the solution.
return the fluid to the IV bag to dissolve the crystals.
Correct answer: B
Rationale: Even though a filter should always be used with this medication infusion, a solution with crystals present in the bag or tubing should never be infused. The nurse should first discard the solution and then restart the infusion with a new bag, ensuring that there is a filter on the IV line.
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27. Potassium-Sparing Diuretics
amiloride (Midamor)
spironolactone (Aldactone)
triamterene (Dyrenium)
Also known as aldosterone-inhibiting diuretics
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28. 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 resorption of sodium and water usually induced by aldosterone
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29. Potassium-Sparing Diuretics: Drug Effects
Prevent potassium from being pumped into the tubule, thus preventing its secretion
Competitively block aldosterone receptors and inhibit their action
Promote the excretion of sodium and water
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30. Potassium-Sparing Diuretics: Indications
spironolactone and triamterene
Hyperaldosteronism
Hypertension
Reversing potassium loss caused by potassium-losing drugs
Certain cases of HF
amiloride
Treatment of HF
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31. Potassium-Sparing Diuretics: Adverse Effects
Body System Adverse Effects
CNS Dizziness, headache
GI Cramps, nausea, vomiting, diarrhea
Other Urinary frequency, weakness, hyperkalemia
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32. Potassium-Sparing Diuretics: Adverse Effects (cont’d)
spironolactone (Aldactone)
Gynecomastia
Amenorrhea
Irregular menses
Postmenopausal bleeding
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33. Thiazide and Thiazide-like Diuretics
Thiazide diuretics
hydrochlorothiazide (Esidrix, HydroDIURIL)
chlorothiazide (Diuril)
Thiazide-like diuretics
metolazone (Mykrox, Zaroxolyn)
chlorthalidone (Hydone, Thalitone)
indapamide (Lozol)
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34. Thiazide and Thiazide-like Diuretics: Mechanism of Action
Inhibit tubular resorption of sodium, chloride, and potassium ions
Action primarily in the distal convoluted tubule
Result: water, sodium, and chloride are excreted
Potassium is also excreted to a lesser extent
Dilate the arterioles by direct relaxation
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35. Thiazide and Thiazide-like Diuretics: Drug Effects
Lowered peripheral vascular resistance
Depletion of sodium and water (and potassium)
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36. Thiazide and Thiazide-like Diuretics (cont’d)
Thiazides should not be used if creatinine clearance is less than 30 to 50 mL/min (normal is 125 mL/min)
Metolazone remains effective to a creatinine clearance of 10 mL/min
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37. Thiazide and Thiazide-like Diuretics: Indications
Hypertension (one of the most prescribed group of drugs for this)
Edematous states
Idiopathic hypercalciuria
Diabetes insipidus
Heart failure due to diastolic dysfunction
Adjunct drugs in treatment of edema related to HF, hepatic cirrhosis, or corticosteroid or estrogen therapy
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38. Thiazide and Thiazide-like Diuretics: Adverse Effects
Body System Adverse Effects
CNS Dizziness, headache, blurred vision
GI Anorexia, nausea, vomiting, diarrhea
GU Impotence
Hematologic Jaundice, leukopenia
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39. Thiazide and Thiazide-like Diuretics: Adverse Effects (cont’d)
Body System Adverse Effects Integumentary Urticaria, photosensitivity Metabolic Hypokalemia, hyperglycemia, hyperuricemia, hypochloremic alkalosis
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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 drugs
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41. Nursing Implications (cont’d)
Instruct patients to take the medication in the morning if possible to avoid interference with sleep patterns
Monitor serum potassium levels during therapy
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42. Nursing Implications (cont’d)
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 drugs
Foods high in potassium include bananas, oranges, dates, apricots, raisins, broccoli, green beans, potatoes, meats, fish, and legumes
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43. Nursing Implications (cont’d)
Patients taking diuretics along with a digitalis preparation should be taught to monitor for digitalis toxicity
Patients with diabetes mellitus who are taking thiazide and/or loop diuretics should be told to monitor blood glucose and watch for elevated levels
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44. Nursing Implications (cont’d)
Teach patients to change positions slowly and to rise slowly after sitting or lying to prevent dizziness and fainting related to orthostatic hypotension
Encourage patients to keep a log of their daily weight
Remind patients to return for follow-up visits and lab work
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45. Nursing Implications (cont’d)
Patients who have been ill with nausea, vomiting, and/or diarrhea should notify their primary care provider because fluid and electrolyte imbalances can result
Signs and symptoms of hypokalemia include muscle weakness, constipation, irregular pulse rate, and overall feeling of lethargy
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46. Nursing Implications (cont’d)
Instruct patients to notify their primary care provider immediately if they experience rapid heart rates or syncope (reflects hypotension or fluid loss)
Excessive consumption of licorice can lead to additive hypokalemia in patients taking thiazides
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47. Nursing Implications (cont’d)
Monitor for adverse effects
Metabolic alkalosis, drowsiness, lethargy, hypokalemia, tachycardia, hypotension, leg cramps, restlessness, decreased mental alertness
Monitor for hyperkalemia with potassium-sparing diuretics
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48. Nursing Implications (cont’d)
Monitor for therapeutic effects
Reduction of edema
Reduction of fluid volume overload
Improvement in manifestations of heart failure
Reduction of hypertension
Return to normal intraocular pressures
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49. Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
Case Study
A patient with a creatinine clearance of 20 mL/min is admitted to the medical surgical unit. The patient is in need of rapid diuresis. Which class of diuretic does the nurse anticipate administering?
Potassium-sparing
Thiazide
Osmotic
Loop
Correct answer: D
Rationale: The loop diuretics provide rapid diuresis because of their rapid onset of action. Loop diuretics are effective for patients with reduced kidney function (creatinine clearance below 25 mL/min).
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Case Study (cont’d)
The patient is ordered furosemide (Lasix). Before administering furosemide, it is most important for the nurse to assess the patient for allergies to which drug class?
Aminoglycosides
Sulfonamides
Macrolides
Penicillins
Correct answer: B
Rationale: The nurse should assess patients receiving furosemide (Lasix) for cross-sensitivity to sulfonamides. Although allergy to sulfonamide antibiotics is listed as a contraindication, analysis of the literature indicates that cross-reaction with the loop diuretics is unlikely to occur. Loop diuretics are commonly given to such patients in clinical practice. The nurse should closely monitor these patients.
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Case Study (cont’d)
Two days after admission, the nurse is reviewing laboratory results of the patient. Which is the most common electrolyte finding resulting from the administration of furosemide (Lasix)?
Hypocalcemia
Hypophosphatemia
Hypokalemia
Hypomagnesemia
Correct answer: C
Rationale: Of all of the adverse effects of furosemide (Lasix) administration, hypokalemia is of serious clinical importance. To prevent hypokalemia, patients often receive potassium supplements along with furosemide. The other electrolyte disturbances listed do not occur as a result of furosemide (Lasix) therapy.
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52. Copyright © 2014 by Mosby, an imprint of Elsevier Inc.
Case Study (cont’d)
The patient is being discharged home with furosemide (Lasix). When providing discharge teaching, which instruction will the nurse include?
Avoid prolonged exposure to the sun.
Avoid foods high in potassium content.
Stop taking the medication if you feel dizzy.
Weigh yourself once a week and report a gain or loss of more than 1 pound.
Correct answer: A
Rationale: Patients taking furosemide (Lasix) should avoid prolonged exposure to the sun because the drug can cause photosensitivity. Although orthostatic hypotension is a possible adverse effect of the medication, patients should not stop taking the medication without consultation with their health care provider. Patients should weigh themselves once a day and report a weight gain or loss of approximately 3 pounds. Patients taking furosemide (Lasix) should be encouraged to eat foods rich in potassium.
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