• The kidneys are vital organs that perform a wide range of functions crucial to maintaining the body’s homeostasis. Their primary roles include filtering waste from the blood, regulating fluid and electrolyte balance, and controlling blood pressure, among other functions.
• Kidney functions:
  1. Filtration and Excretion of Waste Products
  2. Regulation of Fluid and Electrolyte Balance
  3. Regulation of Blood Pressure
  4. Production of Hormones (Erythropoietin, Renin, Vitamin D)
  5. Regulation of Calcium and Phosphate Balance
  6. Detoxification and Metabolism
  7. Maintenance of Blood Osmolarity
  8. Gluconeogenesis
  9. Regulation of Blood Volume
• Healthy kidney function is essential for survival. When the kidneys fail, waste products, excess fluids, and electrolytes accumulate in the body, leading to a dangerous condition called uremia.
• Without proper kidney function, vital processes like blood pressure regulation, red blood cell production, and bone health are also disrupted, leading to multiple organ dysfunctions.
• When kidneys lose function significantly (as in chronic kidney disease or acute kidney injury), dialysis or kidney transplantation may be necessary to replace their filtering functions.
• Drugs that act on the kidneys are primarily used to manage conditions like hypertension, fluid balance, electrolyte disorders, and various kidney diseases.

Classification

• A diuretic is any substance/drug that promotes diuresis, the increased production of urine.
• Diuretics are drugs that promote excretion of Na⁺ and water in urine.

• These drugs act at thick ascending limb of loop of henle.
• Inhibit Na⁺ - K⁺- 2Cl^- cotransport.
• These are also called Loop diuretics.
• Ex: Furosemide, Bumetanide, Torsemide

• These drugs act at early part of the distal convoluted tubule (DCT).
• Inhibit Na⁺- Cl^- symport.
• Thiazides (Benzothiadiazines) are administered orally, have long duration of action and are excreted in urine.
• Ex:
  1. Thiazides (Benzothiadiazines): Chlorthiazide, Hydrochlorothiazide, Hydroflumethiazide, Benzthiazide
  2. Thiazide related drugs: Chlorthalidone, Indapamide, Xipamide, Metlolazone, Clopamide

1. Carbonic anhydrase Inhibitor:
   • They act at proximal convoluted tubule (PCT).
   • Ex: Acetazolamide (It's use is reduced because of its low efficacy)
2. Potassium sparing diuretics:
   • These drugs act at late DCT and collecting tubule (CT).
   • Ex:
     • Aldosterone antagonists: Spironolactone (Synthetic steroid), Eplerenone
     • Renal epithelial Na⁺ channel Inhibitor: Amiloride, Triamterene
3. Osmotic diuretic:
   • They act on entire nephron but the main site of action is in the loop of henle and PCT.
   • Ex: Mannitol, Isosorbide, Glycerol

1. Antidiuretic hormone and its analogues:
   Vasopressin, Desmopressin, Lypressin, terlipressin
2. Natriuretics:
   Thiazides, Amiloride
3. Miscellaneous:
   Carbamazepine, Chlorpropamide, Indomethacin