Summary

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Key Points

• Key Drugs
  • End in “-thiazide”
    • Hydrochlorothiazide
    • Chlorothiazide
    • Methyclothiazide
  • Thiazide-like diuretics
    • Chlorthalidone
    • Indapamide
    • Metolazone
  • Mechanism (Saunders)
    • Remove excess fluid (Diuresis)
      • Act on the early distal convoluted tubule to block the reabsorption of sodium, potassium, and water
        • Water loves sodium, so if more sodium is excreted from the body, more water will also be excreted (diuresis)
      • May act directly on arterioles to cause vasodilation, decreasing blood pressure
      • Weaker diuretic and slower onset than loop diuretics, but thiazides are still fairly potent
      • Will lead to increased urination
        • Contraindicated in patient with renal impairment
          • You can anticipate that renal function will be measured through creatinine and BUN
          • The effectiveness of the thiazide diuretic greatly decreases with a creatinine clearance less than 30 mL/min
        • Watch for signs and symptoms of dehydration
        • Take in the morning to avoid nocturia
        • Closely monitor intake and output in the hospital setting. Report urine output less than 30 mL/hour.
        • Take daily weights
          • Best way to determine fluid retention
  • Clinical Use (Saunders, mictlan)
    • Hypertension
      • Hydrochlorothiazide is often combined with an antihypertensive to control high blood pressure
    • Edema
      • Due to heart failure, liver failure, or kidney failure
  • Side Effects and Adverse Reactions (Saunders, mictlan)
    • Fluid electrolyte imbalances
      • Hypokalemia
        • Can lead to muscle cramps and life-threatening heart arrhythmias
        • Potassium supplementation is often needed, or combination with potassium-sparing diuretic like spironolactone
        • The most serious drug reaction occurs with digoxin, as hypokalemia can cause digitalis toxicity
        • Closely monitor potassium levels and hold the drug if the patient’s potassium level is less than 3.5
      • Hyperglycemia
        • Use cautiously in patients with diabetes mellitus
        • Closely monitor blood glucose levels
      • Hyponatremia
        • Low sodium increases risk of lithium toxicity, so be extremely cautious if patient is taking lithium concurrently (generally lithium and thiazides are not taken together)
      • Hypercalcemia
        • In contrast to loop diuretics, which cause hypocalcemia
      • Hypomagnesemia
      • Hypochloremia
    • Increased lithium levels/toxicity
      • Diuresis causes a compensatory increase in reabsorption of cations at the proximal tubule, which increases lithium levels
    • Hyperuricemia
      • Patients are at an increased risk of gout
    • Photosensitivity
      • Related to sulfa drug structure
    • Sulfa drug (can cause allergy)
    • Orthostatic hypotension
      • Results from volume depletion induced by diuresis