JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD Pharm. D III Year PHARMACOLOGY - II Previous Question Paper (January/February - 2021 - R08)

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

1. High ceiling (Loop) diuretics: Furosemide, Bumetanide, Torsemide.
2. Thiazide and thiazide-like diuretics: Hydrochlorothiazide, Chlorthalidone, Indapamide.
3. Potassium-sparing diuretics:
   • Aldosterone antagonists: Spironolactone, Eplerenone.
   • Epithelial sodium channel inhibitors: Amiloride, Triamterene.
4. Carbonic anhydrase inhibitors: Acetazolamide.
5. Osmotic diuretics: Mannitol, Glycerin.

Mechanism of Action: Thiazides act primarily on the distal convoluted tubule (DCT) by inhibiting the Na+-Cl- symporter (NCC) on the luminal membrane. By blocking the reabsorption of sodium and chloride, they increase the excretion of these ions along with water. They also promote potassium excretion and decrease urinary calcium excretion.

Adverse Effects:

• Electrolyte imbalance: Hypokalemia, hyponatremia, and hypomagnesemia.
• Metabolic effects: Hyperuricemia (can precipitate gout), hyperglycemia (reduced insulin release), and hyperlipidemia (increased LDL and VLDL).
• Others: Photosensitivity, allergic reactions (sulfonamide sensitivity), and sexual dysfunction.

Contraindications:

• Hypersensitivity to sulfonamides.
• Severe renal failure (anuria), as they require renal function to reach the site of action.
• Severe hepatic impairment (risk of hepatic encephalopathy due to electrolyte shifts).
• Gout or history of hyperuricemia.
• Pregnancy (unless for specific indications like pre-eclampsia, as they may reduce placental perfusion).