Pharmacology Chapter 29: Diuretics and Transporters
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Questions and Answers

What is the primary action of thiazide diuretics in the kidneys?

  • They increase Mg2+ reabsorption.
  • They block K+ reabsorption.
  • They promote Na+ and K+ wasting.
  • They inhibit reabsorption of Na+ and Cl−. (correct)

    • Thiazide diuretics can decrease calcium reabsorption in the kidneys.

    False

    Name two conditions for which thiazide diuretics are commonly used.

    high blood pressure, congestive heart failure

    Thiazide diuretics are ____ sensitive Na+-Cl− symporter inhibitors.

    <p>thiazide</p> Signup and view all the answers

    Match the following diuretics to their respective characteristics:

    <p>Loop diuretics = Inhibit Na+ reabsorption at the thick ascending limb Thiazide diuretics = Inhibit Na+ and Cl− reabsorption at the distal convoluted tubule Furosemide = Example of loop diuretic Hydrochlorothiazide = Example of thiazide diuretic</p> Signup and view all the answers

    Which diuretic acts primarily on the Loop of Henle?

    <p>Loop diuretics</p> Signup and view all the answers

    Thiazide diuretics act on the collecting duct of the nephron.

    <p>False</p> Signup and view all the answers

    What is the mechanism of action for loop diuretics?

    <p>Inhibition of Na+/K+/2Cl- co-transporter (NKCC2)</p> Signup and view all the answers

    Loop diuretics primarily increase the concentration of ions in the ______.

    <p>tubule</p> Signup and view all the answers

    Match each type of diuretic with its site of action:

    <p>Osmotic diuretics = Proximal tubules Loop diuretics = Loop of Henle Thiazide diuretics = Early distal tubule Potassium-sparing diuretics = Late distal tubule</p> Signup and view all the answers

    What percentage of the filtered load of Na+ is reabsorbed in the thick ascending limb (TAL)?

    <p>25%</p> Signup and view all the answers

    Carbonic anhydrase inhibitors act on the Loop of Henle.

    <p>False</p> Signup and view all the answers

    Name a common loop diuretic.

    <p>Furosemide</p> Signup and view all the answers

    What ion loss is associated with alkalosis in compensatory actions?

    <p>Cl-</p> Signup and view all the answers

    Digoxin toxicity can result in increased intracellular calcium concentration.

    <p>True</p> Signup and view all the answers

    Which plant is the source of Digoxin?

    <p>Foxglove</p> Signup and view all the answers

    Digoxin acts as an inhibitor of the Na+/K+ _____ pump.

    <p>ATPase</p> Signup and view all the answers

    Which condition can potentiate the effect of Digoxin and increase the risk of cardiac arrhythmias?

    <p>Hypokalaemia</p> Signup and view all the answers

    Match the following components with their respective functions:

    <p>Na+/K+ ATPase pump = Maintains Na+ and K+ gradients Na+/Ca2+ exchanger = Regulates intracellular calcium levels Aldosterone = Increases Na+ reabsorption Aldosterone antagonists = Reduce Na+ reabsorption</p> Signup and view all the answers

    Aldosterone receptor antagonists promote Na+ reabsorption.

    <p>False</p> Signup and view all the answers

    What is the therapeutic window for Digoxin in µg/L?

    <p>0.6-1.2</p> Signup and view all the answers

    What mechanism do thiazides primarily affect in the kidneys?

    <p>Na+/Ca2+ antiporter</p> Signup and view all the answers

    Thiazides increase the clearance of uric acid in patients with gout.

    <p>False</p> Signup and view all the answers

    What condition is NOT listed as a contraindication for thiazide diuretics?

    <p>Dehydration</p> Signup and view all the answers

    Thiazides cause __________ potassium levels while conserving blood calcium.

    <p>low</p> Signup and view all the answers

    Match the following conditions with their effects of thiazide diuretics:

    <p>Hypotension = Contraindication Gout = Increased uric acid levels Hyperglycemia = Associated with chronic administration Hyperkalemia = Not caused by thiazides</p> Signup and view all the answers

    Increased aldosterone activity due to thiazide use primarily leads to:

    <p>Potassium loss</p> Signup and view all the answers

    Thiazides directly inhibit the Na+/Ca2+ antiporter in the distal convoluted tubule.

    <p>False</p> Signup and view all the answers

    What effect do thiazides have on blood calcium levels?

    <p>Conserve or increase</p> Signup and view all the answers

    What adverse effect is primarily associated with potassium-sparing diuretics?

    <p>Hyperkalaemia</p> Signup and view all the answers

    Potassium supplements can be safely prescribed alongside potassium-sparing diuretics.

    <p>False</p> Signup and view all the answers

    Which diuretic type is often used in combination with loop diuretics and thiazides to reduce potassium loss?

    <p>Potassium-sparing diuretics</p> Signup and view all the answers

    Hyperkalaemia can lead to cardiac ______.

    <p>arrhythmias</p> Signup and view all the answers

    Match the following components with their associated actions:

    <p>Aldosterone = Increases Na+/K+ ATPase expression Spironolactone = Blocks aldosterone receptor ENaC = Facilitates sodium transport K+ sparing diuretics = Prevent potassium loss</p> Signup and view all the answers

    Which of the following statements is true regarding ENaC?

    <p>Blocking ENaC reduces Na+ transport.</p> Signup and view all the answers

    Aldosterone is secreted in response to hyponatremia.

    <p>True</p> Signup and view all the answers

    What effect does spironolactone have on sodium and potassium levels?

    <p>Decreases sodium and increases potassium levels</p> Signup and view all the answers

    Study Notes

    Drugs and Membrane Transporters: Renal Transport Systems

    • Renal transport systems are crucial for drug action and excretion.
    • Loop diuretics, thiazide diuretics, and potassium-sparing diuretics affect renal function.

    Learning Objectives

    • Students should understand the site of action, mechanism of action, and side effects of loop, thiazide, and potassium-sparing diuretics.

    Further Reading

    • Medical Physiology, 3rd Edition, Chapter 35 (Transport of Sodium and Chloride, pp 1111-1116)
    • Rang and Dale's Pharmacology, 10th edition, Chapter 29 (The Kidney and Urinary System, pp 402-412)

    Site and Mechanism of Action

    • Diuretic: Site of Action: Mechanism of Action:
    • Osmotic diuretics: Proximal tubules Inhibition of water and Na+ reabsorption
    • Carbonic anhydrase inhibitors: Proximal tubules Inhibition of bicarbonate reabsorption
    • Loop diuretic: Loop of Henle (thick ascending limb) Inhibition of Na+, K+, and Cl− reabsorption
    • Thiazide: Early distal tubule Inhibition of Na+, Cl− co-transport
    • K+ sparing diuretics: Late distal tubule/collecting duct Inhibition of Na+ reabsorption

    Loop Diuretics

    • Example drugs: Furosemide, bumetanide
    • Mechanism: Inhibit the Na+/K+/2Cl− co-transporter (NKCC2) in the thick ascending limb of Henle's loop.
    • This reduces Na+ and Cl− reabsorption.
    • 25% of filtered Na+ is normally reabsorbed in this section, so loop diuretics have a significant effect.
    • This leads to a decrease in the concentration of ions in the tubule and reduced hypertonicity in the surrounding interstitium, which impacts water reabsorption.

    Thiazide Diuretics

    • Example drugs: Hydrochlorothiazide, chlorothiazide, bendroflumethiazide
    • Mechanism: Block the thiazide-sensitive Na+-Cl− symporter in the early distal convoluted tubule.
    • This inhibits Na+ and Cl− reabsorption.
    • Also increase Ca2+ reabsorption in the distal tubule.

    K+ Sparing Diuretics

    • Mechanism: Aldosterone antagonists (e.g., spironolactone, eplerenone) block aldosterone's effect on Na+/K+ATPase and ENaC, reducing Na+ reabsorption and K+ secretion.
    • Na+ channel inhibitors (e.g., amiloride, triamterene) block ENaC, reducing Na+ reabsorption and thus also K+ secretion to a lesser extent.

    Contraindications

    • Thiazides: May worsen gout, renal failure, hypokalemia, and may worsen diabetes.
    • K+ Sparing Diuretics: Hyperkalemia, a potential adverse effect, is a concern when used with other drugs that also elevate potassium levels, such as ACE inhibitors

    Digoxin Toxicity

    • Digoxin inhibits the Na+/K+ ATPase pump, leading to increased intracellular Na+, reduced Na+/Ca2+ exchange and increased intracellular Ca2+.
    • This can cause cardiac arrhythmias.
    • Loop and thiazide diuretics may increase the risk of digoxin toxicity.

    Blood Electrolyte Balance

    • For reference, normal ranges for blood electrolytes (e.g., Na+, K+, Cl-, Ca2+, Mg2+).

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    Drugs and Renal Transport Systems PDF

    Description

    Explore the mechanisms and effects of various diuretics on renal transport systems in this quiz. Understand the action sites and side effects of loop, thiazide, and potassium-sparing diuretics, drawing from the key concepts in medical physiology and pharmacology. Perfect for students aiming to master renal pharmacology.

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