Carbonic Anhydrase Inhibitors (CAIs)

Introduction to Carbonic Anhydrase

• Enzyme Location: Found in kidneys, eyes, other body parts
• Normal Role: helps bring hydrogen ions into the body in exchange for sodium and water. Sodium and water get excreted into the urine.

Mechanism of Action of CAIs

• Inhibition: Decreases hydrogen availability meaning less in the tubules more being reabsorbed.
• Result: Leads to increased water and sodium excretion

Clinical Applications

Glaucoma

• Problem: Buildup of aqueous humor causes increased intraocular pressure, potentially damaging the optic nerve
• CAI Role: Decreases aqueous humor production, reducing pressure

Additional Indications

• Altitude Sickness: Mechanism unclear, but CAIs are effective
• Metabolic Alkalosis: Used when body is too alkaline

Key Indications to Remember

• Glaucoma
• Altitude Sickness
• Metabolic Alkalosis

Therapeutic Effects

• Decreased Sodium Bicarbonate: Alters acid-base balance
• Decreases Intraocular Pressure: By reducing aqueous humor
• Renal Effects: Promotes sodium and water excretion, primarily in proximal tubules

Precautions and Contraindications

• Diuretic Action: Risks fluid and electrolyte imbalances
• Contraindications: Severe renal/hepatic dysfunction, pre-existing electrolyte imbalances (e.g., hyponatremia, hypokalemia)

Side Effects

• Acidosis: Lower circulating sodium bicarbonate increases acidosis risk
• Other Side Effects: Hypokalemia, drowsiness, paresthesias (numbness/tingling in fingers)

Nursing Actions

• Assessments:
  • Blood pressure
  • Input/output levels
  • Creatinine, potassium, magnesium, sodium levels
  • Acid-base balance

Drug Example

• Acetazolamide: The primary drug to remember in the CAI class