Diuretics: Concept, Classification, Indications, Contraindications, and Adverse Effects

1. Concept:

Diuretics are a group of medications that increase urine production by promoting the excretion of excess water and electrolytes (primarily sodium). This mechanism helps reduce fluid retention (edema), lower blood pressure, and improve kidney function. Diuretics work by interfering with the normal reabsorption of water and electrolytes in the kidneys.

2. Classification:

Diuretics are classified based on their mechanism of action and the site of action within the kidney:

Carbonic Anhydrase Inhibitors:

• Mechanism: Inhibit carbonic anhydrase in the proximal convoluted tubule, reducing the reabsorption of sodium, bicarbonate, and water.
• Examples: Acetazolamide, Methazolamide, Dorzolamide

Thiazide Diuretics:

• Mechanism: Inhibit the reabsorption of sodium and chloride in the distal convoluted tubule.
• Examples: Hydrochlorothiazide, Chlorthalidone, Indapamide

Loop Diuretics:

• Mechanism: Inhibit the reabsorption of sodium and chloride in the loop of Henle.
• Examples: Furosemide, Bumetanide, Torsemide

Potassium-Sparing Diuretics:

• Mechanism: Increase sodium excretion without causing a decrease in potassium levels.
• Examples: Spironolactone, Amiloride, Triamterene

3. Indications:

a. Carbonic Anhydrase Inhibitors:

• Less frequently used as diuretics:
  • Due to frequent and potentially dangerous side effects.
• Glaucoma: Reduce intraocular pressure by decreasing fluid in the eye.
• Epilepsy: Reduce cerebrospinal fluid production, helping to control seizures.

b. Thiazide Diuretics:

• Edema in Heart, Liver, and Kidney Failure: Reduce edema caused by heart failure, liver failure, and kidney failure.
• Hypertension: Lower blood pressure by decreasing the amount of water and salt in the body.
• Idiopathic Hypercalciuria: Reduce calcium levels in urine, helping to treat kidney stones.

c. Loop Diuretics:

• Edema of Various Origins, Hypertension: Reduce edema caused by heart failure, liver failure, kidney failure, and hypertension.
• Severe Edema, Acute Pulmonary Edema, Hypertension Crisis, Hypercalcemia: Act rapidly and powerfully, helping to address acute conditions.
• Acute Poisoning: Eliminate toxins from the body.

4. Contraindications:

a. Carbonic Anhydrase Inhibitors:

• Chronic Lung Disease: May cause metabolic acidosis, worsening the condition.
• Chronic Obstructive Pulmonary Disease (COPD): May cause respiratory depression.
• Cirrhosis and Liver Failure (causing hepatic coma):
  • May cause metabolic acidosis, worsening liver failure.

b. Thiazide Diuretics:

• Hypokalemia in Patients with Cirrhosis Receiving Digoxin:
  • May cause digitalis toxicity.
• Gout: May increase uric acid levels, leading to gout attacks.
• Liver Failure, Kidney Failure, Sulfa Allergy:
  • May be toxic to the liver and kidneys.
• Drug Allergy:
  • May cause severe allergic reactions.
• Urinary Tract Obstruction:
  • May increase pressure in the urinary tract, worsening obstruction.

c. Loop Diuretics:

• Dehydration and Hypovolemia (Hyponatremia):
  • May worsen dehydration and hyponatremia.
• Allergy:
  • May cause severe allergic reactions.
• Non-Responsive to Treatment:
  • If a patient doesn’t respond to loop diuretic treatment, a different medication might be needed.
• Pre-Hepatic Coma or Hepatic Coma:
  • May cause metabolic acidosis, worsening hepatic coma.
• Anuria or Kidney Failure in Poisoning:
  • May further stress the kidneys, worsening kidney failure.
• Obstruction: Stones, Benign Prostatic Hyperplasia, etc.:
  • May increase pressure in the urinary tract, worsening obstruction.

5. Adverse Effects:

a. Carbonic Anhydrase Inhibitors:

• Metabolic Acidosis: Due to inhibition of bicarbonate reabsorption.
  • Note: Use intermittently to avoid metabolic acidosis.
• Hypokalemia: May cause fatigue and increase susceptibility to digitalis toxicity.

b. Thiazide Diuretics:

• Hyponatremia, Hypokalemia:
  • May cause dehydration, hyponatremia, and hypokalemia.
• Hyperuricemia:
  • May trigger gout attacks.
• Exacerbation of Diabetes Mellitus:
  • May increase blood sugar levels.
• Increase in Cholesterol and LDL Levels (5-15% -> Hyperlipidemia):
  • May increase the risk of cardiovascular disease.
• Allergy:
  • May cause severe allergic reactions.

c. Loop Diuretics:

• Fatigue, Cramps, Pre-Hepatic Coma, Hypotension (due to rapid excretion):
  • May cause dehydration, hypotension, metabolic acidosis, and worsen liver failure.
• Hyperuricemia, Hyperglycemia:
  • May trigger gout attacks and worsen diabetes.
• Metabolic Alkalosis with Long-Term Use:
  • May cause acid-base imbalance.
• Hypomagnesemia, Hypocalcemia:
  • May cause electrolyte imbalance.
• Blood Dyscrasia (May Cause Bleeding):
  • May cause anemia.
• Decrease in WBC and RBC Counts:
  • May impair immune function.
• Hepatic and Renal Toxicity, Skin Rash, Numbness:
  • May be toxic to the liver and kidneys.
• Toxicity to Cranial Nerve VIII:
  • May cause damage to the eighth cranial nerve.

Notes:

• Diuretics are often used in combination with other medications, such as antihypertensives.
• Close monitoring of the patient’s condition is essential, especially blood pressure, potassium levels, weight, and urine output.
• Always take diuretics as prescribed by a doctor and avoid self-medication.
• Avoid long-term use of diuretics without a doctor’s prescription.

Conclusion:

Diuretics are a critical group of medications in treating various conditions involving fluid and electrolyte retention. However, it’s crucial to use them cautiously and follow a doctor’s instructions to prevent adverse effects.