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DIURETICS

DIURETICS. Prof. Hanan Hagar Pharmacology Unit. Classification of diuretics. Carbonic Anhydrase Inhibitors Loop Diuretics Thiazides Potassium-Sparing Diuretics Osmotic Diuretics. Loop Diuretics. LOOP DIURETICS High Ceiling diuretics.

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DIURETICS

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  1. DIURETICS Prof. Hanan Hagar Pharmacology Unit

  2. Classification of diuretics • Carbonic Anhydrase Inhibitors • Loop Diuretics • Thiazides • Potassium-Sparing Diuretics • Osmotic Diuretics

  3. Loop Diuretics

  4. LOOP DIURETICSHigh Ceiling diuretics • The most potent diuretic, termed “high ceiling diuretic” Efficacy: High natriuresis as 25-30% Na+ is reabsorbed. • Drugs as: • Furosemide - Torsemide • Bumetanide – Ethacrynic acid

  5. Loop DiureticsHigh Ceiling Diuretics Ethacrynic Acid Potency 0.7, t½ 1h Bumetanide Potency40 ,t½ 0.8 h Torsemide Potency 3, t½ 3.5h Furosemide Potency 1, t½ 1.5h

  6. LOOP DIURETICS Mechanism: • inhibit Na+ / K+ / 2 Cl- co-transporter in the luminal membrane of the thick ascending loop of Henle (TAL). • inhibit Ca++ and Mg ++ re-absorption.

  7. Ascending loop of Henle • Is impermeable to water • In thick ascending loop of Henle (TAL)is responsible for active re-absorption of Na, K and Cl (25-30% Na+ is reabsorbed) via transport system in luminal membrane called Na+/ K+ / 2Cl- co-transporter • Ca and Mg are reabsorbed and enter the interstitial fluid via paracellular pathway

  8. Ascending loop of Henle

  9. Ascending loop of Henle

  10. Pharmacokinetics • Given orally or I. V. • Have fast onset of action (suitable for emergency) • Have short duration of action. • Excreted by active tubular secretion of weak acids into urine • Interfere with uric acid secretion (hyperuricemia).

  11. Pharmacological effects: • ↑ urinary excretion of Na+ and K+ • ↑ urinary excretion Ca++ and Mg ++ • ↑ urine volume • ↑ renal blood flow.

  12. Uses: are drug of choice for emergency situations as: • Edema associated with congestive heart failure, nephrotic syndrome • Acute pulmonary edema • Acute hyperkalaemia. • Acute hypercalcemia

  13. ADVERSE EFFECTS Metabolic Alkalosis Volume Depletion Ototoxicity Hypokalemia Hyperuricemia Hypocalcaemia Hypomagnesaemia Hyperglycemia

  14. Loop diuretics Drug- drug interactions ↓Diuretic Response NSAIDS Arrhythmias Digitalis ↑Ototoxicity of Loop Diuretic Aminoglycosides

  15. Adverse effects : • Hypovolemia • Hyponatraemia (↓ blood Na+). • Hypokalemia (↓ blood K+) • Hypomagnesaemia (↓ blood Mg2+) • Hypocalcaemia (↓ blood Ca2+) • Metabolic alkalosis. • Postural hypotension • Dietary K supplementation or K-sparing diuretics should be used to avoid hypokalemia .

  16. Adverse effects : • Hyperuricemia (increase blood uric acid and gouty attack). • Ototoxicity (risk increased if combined with aminoglycosides) • Allergic reactions

  17. Thiazide diuretics Drugs as: • Chlorothiazide • Hydrochlorothiazide • Chlorthalidone • Metolazone • Indapamide

  18. Thiazide diuretics Chlorthalidone Potency 10, t½ 26h Chlorothiazide Potency 0.1, t½ 2h Metolazone Potency 5, t½ 5h Hydrochlorothiazide Potency 1 , t½ 3h Indapamide Potency 20, t½ 16h

  19. Thiazide diuretics Mechanism of action: • acts via inhibition of Na/Cl co-transporter on the luminal membrane of distal convoluted tubules. • Efficacy: Moderate natriuresis (5-10% of filtered load of sodium is reabsorbed).

  20. Distal convoluted tubules

  21. Mechanism of action of thiazide diuretics

  22. Pharmacokinetics: • Given orally, slow of onset • long duration of action (40 h) • are secreted by active tubular secretory system of the kidney • may interfere with uric acid secretion and cause hyperuricemia

  23. Pharmacological effects: urinary NaCl excretion urinary K excretion (Hypokalemia) urinary magnesium excretion urinary calcium excretion calcium re-absorption hypercalcemia

  24. Thiazide diuretics

  25. Uses: • Treatment of essential hypertension (cheap-well tolerated). • Treatment of mild heart failure (to reduce extracellular volume). • Treatment of osteoporosis

  26. Uses: • Calcium nephrolithiasis due to hypercalciuria(to increase calcium re-absorption and decrease renal calcium stones) • Nephrogenic diabetes insipidus (decrease blood volume and GFR)

  27. Mechanism of antidiuretic effect of thiazide in diabetes insipidus Thiazide Urine volume Distal delivery of Na+ & water Distal tubular Na+ reabsorption Urinary excretion Proximal Na+ & Water reabsorption Extracellular volume

  28. Adverse effects: • Fluid and electrolyte imbalance • Hyponatremia • Hypovolemia (volume depletion) • Hypokalemia • Metabolic alkalosis. • Hyperuricaemia (gout) • Hypercalcemia • Hyperglycaemia • Hyperlipidemia

  29. ADVERSE EFFECTS Metabolic Alkalosis Volume Depletion Hypokalemia Hyperuricemia Hypocalcaemia Hypomagnesaemia Hyperglycemia Hyperlipidemia

  30. Thiazide diuretics Drug- drug interactions Thiazides Diminish effect Uricosurics Sulphonylurea Thiazides Increase effect Digitalis Diazoxide Reduce thiazide efficacy NSAIDs https://www.youtube.com/watch?v=9OBvNpnS0h4

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