NURS 3210 CH 28 PPT

Diuretics

• Classified according to their sites of action within the nephron, chemical structure, and diuretic potency
• Types of diuretic drugs:
  • Carbonic anhydrase inhibitors (CAIs)
  • Loop diuretics
  • Osmotic diuretics
  • Potassium-sparing diuretics
  • Thiazide and thiazide-like diuretics

Carbonic Anhydrase Inhibitors (CAIs)

• Chemical derivative of sulfonamide antibiotics
• Inhibit the activity of the enzyme carbonic anhydrase
• Found in kidneys, eyes, and other parts of the body
• Acetazolamide (Diamox) is the most commonly used CAI
• Mechanism of action:
  • Block the action of carbonic anhydrase, preventing the exchange of H+ ions with sodium and water
  • Inhibition of carbonic anhydrase reduces H+ ion concentration in renal tubules
  • Dilate arterioles by direct relaxation

Loop Diuretics

• Most commonly used loop diuretic: Furosemide (Lasix)
• Uses:
  • Pulmonary edema
  • Edema associated with heart failure (HF), liver disease, nephrotic syndrome, ascites, and hypertension
• Important to determine if the patient is also taking lithium, as it can increase the risk of lithium toxicity

Osmotic Diuretics

• Most commonly used osmotic diuretic: Mannitol (Osmitrol)
• 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, producing rapid diuresis
• Drug effects:
  • Increases glomerular filtration rate and renal plasma flow
  • Helps to prevent kidney damage during acute renal failure (ARF)
  • Reduces intracranial pressure or cerebral edema associated with head trauma
  • Reduces excessive intraocular pressure
• Indications:
  • Treatment of patients in the early, oliguric phase of ARF
  • To promote excretion of toxic substances
  • To reduce intracranial pressure
  • Treatment of cerebral edema
• Adverse effects:
  • Convulsions
  • Thrombophlebitis
  • Pulmonary congestion

Potassium-Sparing Diuretics

• Examples:
  • Amiloride (Midamor)
  • Spironolactone (Aldactone)
  • Triamterene (Dyrenium)
• 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
• 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
• Indications:
  • Spironolactone and triamterene:
    • Hyperaldosteronism
    • Hypertension
    • Reversing potassium loss caused by potassium-losing drugs
    • Certain cases of HF: prevention of remodeling
  • Amiloride:
    • Similar to spironolactone and triamterene, but less effective in the long term
• Adverse effects:
  • Body system:
    • CNS: dizziness, headache
    • GI: cramps, nausea, vomiting, diarrhea
    • Other: urinary frequency, weakness, hyperkalemia
  • Spironolactone (Aldactone):
    • Gynecomastia
    • Amenorrhea
    • Irregular menses
    • Postmenopausal bleeding

Thiazide and Thiazide-Like Diuretics

• Examples:
  • Thiazide diuretics: hydrochlorothiazide (Esidrix, HydroDIURIL), chlorothiazide (Diuril)
  • Thiazide-like diuretics: metolazone (Mykrox, Zaroxolyn), chlorthalidone (Hydone, Thalitone), indapamide (Lozol)
• 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, and potassium is also excreted to a lesser extent
• Drug effects:
  • Lowered peripheral vascular resistance
  • Depletion of sodium and water (and potassium)
  • 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
• Indications:
  • Hypertension (one of the most prescribed group of drugs for this)
  • Edematous states
  • Idiopathic hypercalciuria
  • Diabetes insipidus
  • Adjunct drugs in management of heart failure and hepatic cirrhosis
• Adverse effects:
  • Body system:
    • CNS: dizziness, headache, blurred vision
    • GI: anorexia, nausea, vomiting, diarrhea
    • Genitourinary: impotence
    • Hematologic: jaundice, leukopenia
    • Integumentary: dizziness, headache, blurred vision
    • Metabolic: hypokalemia, hyperglycemia, hyperuricemia, hypochloremic alkalosis

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 blood pressure)
• Assess for disorders that may contraindicate or necessitate cautious use of these drugs