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Diuretics Pharmacology Reference

1. Acetazolamide (Carbonic Anhydrase Inhibitors)

• Site: Proximal Convoluted Tubule (PCT).
• Mechanism: Inhibits carbonic anhydrase. Prevents NaHCO3 reabsorption.
• Effects: NaHCO3 diuresis, ↑ Urine pH, ↓ Blood pH (Metabolic Acidosis).
• Clinical Use: Glaucoma, Altitude Sickness, Metabolic Alkalosis, Pseudotumor Cerebri.
• Adverse Effects: Acidosis (Type 2 RTA), Paresthesias, NH3 toxicity (avoid in hepatic encephalopathy), Sulfa allergy.

2. Mannitol (Osmotic Diuretics)

• Site: PCT and Descending Limb of Loop.
• Mechanism: Increases tubular osmolarity, holds water in tubule.
• Adverse Effects: Pulmonary Edema (initial volume expansion), Dehydration (Hypernatremia). Contraindicated in CHF/Anuria.

3. Loop Diuretics (Furosemide, Bumetanide)

• Site: Thick Ascending Limb (Loop of Henle).
• Mechanism: Inhibits Na+/K+/2Cl- cotransporter. Abolishes medullary hypertonicity. Stimulates PGE (vasodilation).
• Effects: "Loops Lose Calcium". Potent diuresis.
• Adverse Effects (OH H DANG): Ototoxicity, Hypokalemia, Hypomagnesemia, Dehydration, Allergy (Sulfa), Alkalosis, Nephritis, Gout.
• Note: Ethacrynic Acid is non-sulfa but MORE ototoxic.

4. Thiazides (HCTZ, Chlorthalidone)

• Site: Distal Convoluted Tubule (DCT).
• Mechanism: Inhibits Na+/Cl- cotransporter. Increases Ca2+ reabsorption.
• Adverse Effects (HyperGLUC): HyperGlycemia, HyperLipidemia, HyperUricemia, HyperCalcemia. Also Hypokalemic Metabolic Alkalosis, Hyponatremia.

5. K+-Sparing Diuretics

• Site: Cortical Collecting Duct.
• Aldosterone Antagonists: Spironolactone (Gynecomastia), Eplerenone.
• ENaC Blockers: Triamterene, Amiloride (Use for Liddle's).
• Effect: Hyperkalemia, Metabolic Acidosis (Type 4 RTA).

Electrolyte Cheat Sheet

Drug	Urine Na+	Urine K+	Blood pH	Blood Ca2+
Acetazolamide	↑	↑	↓ (Acid)	-
Loops	↑↑↑	↑	↑ (Alk)	↓ (Hypo)
Thiazides	↑↑	↑	↑ (Alk)	↑ (Hyper)
K+-Sparing	↑	↓	↓ (Acid)	-