Thiazide and Thiazide-like Diuretics

Mechanism of Action

• Inhibit reabsorption of sodium, potassium, and chloride in the distal tubule.
• Direct dilation of peripheral arterioles leading to decreased peripheral vascular resistance.
  • Arterioles: Small branches of an artery leading into capillaries, supplying oxygen-rich blood.

Therapeutic Effects

• Increased excretion of:
  • Water (H2O)
  • Sodium
  • Potassium
  • Chloride
• Without altering pH.
• Peripheral arterial dilation leading to:
  • Less peripheral vascular resistance.
  • Decreased afterload (less resistance for the left ventricle).

Indications

• High blood pressure (hypertension)
• Heart failure
• Fluid overload and edema

Precautions

• Impaired renal function
• Pre-existing dehydration
• Pre-existing electrolyte disturbance

Contraindications

• Chronic renal failure
• Untreated dehydration or electrolyte disturbances, specifically hypokalemia

Side and Adverse Effects

• Electrolyte disturbances:
  • Decreased potassium levels
  • Potentially increased calcium levels
• Common side effects:
  • Headache
  • Dizziness
  • Impotence in men
• Significant side effects:
  • Increases in lipids, glucose, and uric acid levels
    • Notable increase in glucose (possible insulin resistance or inhibited glucose uptake)
  • Decreased excretion of lithium
    • Lithium used for bipolar disorder treatment

Nursing Actions

• Monitor:
  • Blood pressure
  • Intake and output (I's and O's)
  • Renal function (BUN and creatinine levels)
  • Potassium, magnesium, and calcium levels

Examples of Drugs in the Class

• Hydrochlorothiazide
• Metolazone (less commonly seen)

Key Points

• Remember increase in glucose and decreased lithium excretion.
• Monitor relevant blood and electrolyte levels when administering these medications.