Diuretics

Diuretics

1. Increases urination by decreasing reabsorption of ions like sodium

   • Water is pulled by the ions via passive transport

2. Used to treat edema, HTN, and glaucoma

3. Thiazide Diuretics

   • Most common of all diuretics
   • Most common: HCTZ
     • Others: metolazone; chlorthalidone; indapamide
   • Affects the distal tubule
   • Inhibits the Na/Cl co-transporter
     • Increases excretion of Na, Cl, K, and Mg
     • Less Ca excretion
     • Reduced peripheral vascular resistance
   • Used to treat HTN, diabetes insipidus, hypercalciuria, and heart failure
   • Taken orally for 1-3 wks to decrease BP
   • Secreted by the kidneys
   • Side effects: hyperuremia (and gout), hyponatremia; hypokalemia; volume depletion; hyperglycemia; hyperlipidemia

4. Osmotic Diuretics

   • Carry water as they are filtered through the glomerulus
   • Mannitol is the most common
   • Increases water excretion, but not sodium excretion
   • Prevents acute renal failure and increased intracranial pressure

5. Potassium-Sparing Diuretics

   • Acts on collecting tubule
   • Inhibits Na reabsorption and K excretion
     • Caution in renal disease patients: increased risk for hyperkalemia
   • Used to treat HTN, but with a thiazide
   • Aldosterone Antagonists
     • Prevent proteins from stimulating Na/K exchange sites
       • Blocking aldosterone should relieve edema
     • Spironolactone and eplerenone
     • Used as a diuretic and in heart failure
     • Highly bound to plasma proteins
     • Side effects: GI upsets; mimicry of sex hormones
   • Sodium Channel Blockers
     • Triamterene and amiloride
     • Blocks sodium transport channels, decreasing Na/K exchange
     • Side effects: K retention; renal stones, increased uric acid

6. Loop Diuretics

   • Causes the most diuresis
     • Useful in emergency situations
   • Acts on ascending loop of Henle
   • Most common is furosemide; others are bumetanide and torsemide
   • Inhibits Na/K/2Cl cotransport, reducing reabsorption
     • Increases excretion of Na, K, and Ca
     • Decreases renal vascular resistance
       • Increases renal blood flow
     • Increases prostaglandin synthesis - may increase renal blood flow
   • Used in treating acute pulmonary edema in heart failure
   • Used to treat hyperkalemia nd hypercalcemia
   • Side effects: ototoxicity; hypermagnesemia; hyperurecemia; potassium depletion

7. Carbonic Anhydrase Inhibitors

   • Acetazolamide and methazolamide
   • Weak diuretic
   • Works on proximal tubule
   • Decreases ability to exchange Na for H for bicarbonate
   • Used to treat glaucoma
     • Acetazolamide (Diamox) 2 250mg tablets
     • Dorzolamide and brinzolamide are used topically
   • Also treats pseudotumor cerebri and mountain sickness
   • Side effects: metabolic acidosis, K depletion, renal stones, drowsiness, paresthesia
   • Avoid in patients with cirrhosis