Chapter 44
Diuretics
Introduction to Diuretics
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How diuretics work: Mechanism of action
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Site of action
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Blockade of sodium and chloride reabsorption
Proximal tubule produces greatest diuresis
Adverse effects
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Hypovolemia
Acid-base imbalance
Electrolyte imbalances
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Introduction to Diuretics
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Classification of diuretics
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Four major categories
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Loop: Furosemide
Thiazide: Hydrochlorothiazide
Osmotic: Mannitol
Potassium-sparing: Two subcategories
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Aldosterone antagonists (spironolactone)
Nonaldosterone antagonists (triamterene)
Fifth group
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Carbonic anhydrase inhibitors
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Loop Diuretics
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Furosemide (Lasix): Most frequently
prescribed loop diuretic
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Mechanism of action
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Pharmacokinetics
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Acts on ascending loop of Henle to block reabsorption
Rapid onset (PO 60 min; IV 5 min)
Therapeutic uses
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Pulmonary edema
Edematous states
Hypertension
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Furosemide [Lasix]
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Adverse effects
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Hyponatremia, hypochloremia, and dehydration
Hypotension
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Loss of volume
Relaxation of venous smooth muscle
Hypokalemia
Ototoxicity
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Furosemide [Lasix]
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Adverse effects (Cont.)
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Hyperglycemia: happens mostly in diabetics
Hyperuricemia
Use in pregnancy
Impact on lipids, calcium, and magnesium
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Furosemide [Lasix]
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Drug interactions
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Digoxin
Ototoxic drugs
Potassium-sparing diuretics
Lithium
Antihypertensive agents
Nonsteroidal antiinflammatory drugs
Preparations, dosage, and administration
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Oral
Parenteral
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Other High-Ceiling (Loop) Diuretics
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Ethacrynic acid [Edecrin]
Bumetanide [Bumex]
Torsemide [Demadex]
All can cause:
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Ototoxicity, hypovolemia, hypotension,
hypokalemia, hyperuricemia, hyperglycemia, and
disruption of lipid metabolism
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Thiazides and Related Diuretics
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Also known as benzothiadiazides
Effects similar to those of loop diuretics
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Increase renal excretion of sodium, chloride,
potassium, and water
Elevate levels of uric acid and glucose
Maximum diuresis is considerably lower than
with loop diuretics
Not effective when urine flow is scant (unlike
with loop diuretics)
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Hydrochlorothiazide [HydroDIURIL]
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Hydrochlorothiazide [HydroDIURIL]
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Most widely used
Action: Early segment distal convoluted tubule
Peaks in 4-6 hours
Therapeutic uses
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Essential hypertension
Edema
Diabetes insipidus (lose lots of fluids constantly, thirsty)
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Hydrochlorothiazide [HydroDIURIL]
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Adverse effects
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Hyponatremia, hypochloremia, and dehydration
Hypokalemia
Use in pregnancy and lactation
Hyperglycemia
Hyperuricemia
Impact on lipids, calcium, and magnesium
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Hydrochlorothiazide [HydroDIURIL]
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Drug interactions
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Digoxin
Augments effects of hypertensive medications
Can reduce renal excretion of lithium (leading to
accumulation)
NSAIDs may blunt diuretic effect
Can be combined with ototoxic agents without
increased risk of hearing loss
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Potassium-Sparing Diuretics
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Useful responses
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Rarely used alone for therapy
Aldosterone antagonist
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Modest increase in urine production
Substantial decrease in potassium excretion
Spironolactone
Nonaldosterone antagonists
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Triamterene
Amiloride
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Spironolactone [Aldactone]
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Mechanism of action
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Blocks aldosterone in the distal nephron
Retention of potassium
Increased excretion of sodium
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Spironolactone [Aldactone]
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Therapeutic uses
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Hypertension
Edematous states
Heart failure (decreases mortality in severe failure)
Primary hyperaldosteronism
Premenstrual syndrome
Polycystic ovary syndrome
Acne in young women
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Spironolactone [Aldactone]
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Adverse effects
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Hyperkalemia
Benign and malignant tumors
Endocrine effects
Drug interactions
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Thiazide and loop diuretics
Agents that raise potassium levels
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Osmotic Diuretic
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Mannitol [Osmitrol]
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Promotes diuresis by creating osmotic force within
lumen of the nephron
Pharmacokinetics
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Drug must be given parenterally
Therapeutic uses
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Prophylaxis of renal failure
Reduction of intracranial pressure
Reduction of intraocular pressure
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Mannitol [Osmitrol]
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Adverse effects
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Edema
Headache
Nausea
Vomiting
Fluid and electrolyte imbalance
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Question 1
When providing discharge teaching for a patient who has been
prescribed furosemide [Lasix], it is most important for the nurse to
include which dietary items to prevent adverse effects of
furosemide [Lasix] therapy?
A.
B.
C.
D.
Oranges, spinach, and potatoes
Baked fish, chicken, and cauliflower
Tomato juice, skim milk, and cottage cheese
Oatmeal, cabbage, and bran flakes
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Question 2
A patient is prescribed spironolactone [Aldactone] for treatment
of hypertension. Which foods should the nurse teach the patient to
avoid?
A.
B.
C.
D.
Baked fish
Low-fat milk
Salt substitutes
Green beans
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Question 3
The nurse cares for a patient who is prescribed oral bumetanide
twice daily. It is most important for the nurse to take which action?
A.
B.
C.
D.
Monitor the patient for signs and symptoms of hyperkalemia.
Insert a urinary catheter and assess the hourly urine output.
Weigh the patient before administering each dose.
Schedule the medication to be given at 0800 and 1400.
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Question 4
A patient with heart failure who takes furosemide [Lasix] is
diagnosed with bacterial pneumonia. Which medication, if ordered
by the physician, should the nurse question?
A.
B.
C.
D.
Ciprofloxacin [Cipro]
Gentamicin [Garamycin]
Amoxicillin [Amoxcil]
Erythromycin [E-Mycin]
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