90 Questions
What is the primary mechanism of calcium reabsorption in the tubule?
Passage through a channel and then transported by a Na+/Ca2+ exchanger into the interstitial fluid
What is the effect of thiazide diuretics on urinary calcium excretion?
Thiazide diuretics decrease urinary calcium excretion
Which of the following is NOT a therapeutic use of thiazide diuretics?
Diabetes insipidus
What is the effect of thiazide diuretics on potassium levels?
Thiazide diuretics decrease potassium levels
Which of the following is a thiazide-like diuretic?
Chlorthalidone
What is the mechanism of action of thiazide diuretics?
Inhibition of a Na+/Cl− cotransporter
What is the effect of thiazide diuretics on peripheral vascular resistance?
Thiazide diuretics decrease peripheral vascular resistance
Why are thiazide diuretics sometimes called “low ceiling diuretics”?
Because increasing the dose above normal therapeutic doses does not promote further diuretic response
Which of the following is a consequence of chronic use of thiazide diuretics in elderly patients?
Magnesium deficiency
What is the primary mechanism of action of loop diuretics in the ascending limb of the loop of Henle?
Inhibition of the cotransport of Na+/K+/2Cl−
Which of the following is a unique ability of thiazide diuretics?
Producing a hyperosmolar urine
What is the effect of loop diuretics on urinary calcium excretion?
Increase urinary calcium excretion
What is the primary use of thiazide diuretics in the treatment of idiopathic hypercalciuria?
To inhibit urinary Ca2+ excretion
What is the effect of thiazide diuretics on serum potassium levels?
Decrease serum potassium levels
What is the effect of loop diuretics on left ventricular filling pressures?
Decrease left ventricular filling pressures
What is the primary difference between the pharmacokinetics of thiazide and loop diuretics?
Thiazides take weeks to produce a stable reduction in blood pressure, while loop diuretics act rapidly
What is the primary use of loop diuretics in the treatment of heart failure?
To reduce extracellular volume
What is the effect of thiazide diuretics on serum uric acid levels?
Increase serum uric acid levels
What is the name of the structure that filters the blood entering the kidneys?
Glomerulus
What percentage of the filtered sodium is reabsorbed in the proximal convoluted tubule?
Two-thirds
What is the purpose of the Na+/K+-adenosine triphosphatase (ATPase) pump in the proximal convoluted tubule?
To maintain normal levels of sodium and potassium in the cell
What is the characteristic of the ascending loop of Henle?
It is impermeable to water
What is the mechanism of active reabsorption of Na+, K+, and Cl− in the ascending loop of Henle?
Na+/K+/2Cl− cotransporter
What is the characteristic of the distal convoluted tubule?
It is impermeable to water
What is the mechanism of reabsorption of sodium chloride in the distal convoluted tubule?
Na+/Cl− transporter
What is the effect of diuretics on the organic acid secretory system?
They compete with organic acids for transfer
What is the definition of diuretics?
Drugs that increase the volume of urine
What is the primary effect of spironolactone on androgen levels in polycystic ovary syndrome?
Blocks androgen receptors
What is the most common side effect of spironolactone?
Hyperkalemia
What is the mechanism of action of triamterene and amiloride?
Blockage of Na+ transport channels
What is the effect of acetazolamide on phosphate excretion?
Increased phosphate excretion
What is the therapeutic use of acetazolamide in altitude sickness?
Prevention of symptoms of altitude sickness
What is the mechanism of action of osmotic diuretics?
Increase in urinary osmolarity
What is the primary use of osmotic diuretics?
Maintenance of urine flow in acute renal failure
What is the effect of acetazolamide on urinary pH?
Increase in urinary pH
What is the effect of spironolactone on potassium levels?
Increase in potassium levels
What is the primary indication for the use of loop diuretics in edema?
Pulmonary edema and acute/chronic peripheral edema caused by heart failure or renal impairment
Which of the following adverse effects is associated with the use of ethacrynic acid?
Ototoxicity
What is the mechanism of action of spironolactone in the collecting tubule?
Inhibiting aldosterone at intracellular cytoplasmic receptor sites
What is the effect of spironolactone on Na+ and K+ in edematous states?
Retention of K+ and excretion of Na+
What is the therapeutic use of spironolactone in patients with hepatic cirrhosis?
Treatment of edema associated with secondary hyperaldosteronism
What is the effect of loop diuretics on urinary Ca2+ excretion?
Increase Ca2+ excretion
What is the primary indication for the use of aldosterone antagonists in heart failure?
To prevent myocardial remodeling mediated by aldosterone
What is the adverse effect of loop diuretics that can be corrected by oral supplementation?
Hypomagnesemia
What is the effect of potassium-sparing diuretics on Na+ reabsorption and K+ excretion in the collecting tubule?
Inhibit Na+ reabsorption and K+ excretion
What is the primary function of the Na+/K+-adenosine triphosphatase (ATPase) pump in the proximal convoluted tubule?
To maintain normal levels of Na+ and K+ in the cell
What happens to the osmolarity of the filtrate along the descending portion of the loop of Henle?
It increases
What is the purpose of the organic acid secretory system in the proximal convoluted tubule?
To secrete organic acids like uric acid
What is the effect of diuretic drugs on the organic acid secretory system?
They compete with organic acids for transfer
What is the characteristic of the ascending loop of Henle?
It is impermeable to water and reabsorbs Na+, K+, and Cl−
What is the mechanism of reabsorption of sodium chloride in the distal convoluted tubule?
Via a Na+/Cl− transporter
What percentage of the blood entering the kidneys is filtered into Bowman's capsule?
16-20%
What is the primary function of the distal convoluted tubule?
To reabsorb sodium chloride
What is the purpose of the cup-shaped structure called Bowman's capsule in the renal corpuscle?
To filter the blood entering the kidneys
What is a unique ability of thiazide diuretics in the treatment of nephrogenic diabetes insipidus?
To produce a hyperosmolar urine
What is the effect of loop diuretics on left ventricular filling pressures?
Decrease left ventricular filling pressures
What is a common adverse effect of thiazide diuretics?
Hypokalemia
What is the primary use of loop diuretics in the treatment of heart failure?
To reduce extracellular volume
What is the mechanism of action of loop diuretics in the ascending limb of the loop of Henle?
Inhibition of the cotransport of Na+/K+/2Cl−
What is a characteristic of the dose-response curve of loop diuretics?
A sigmoidal (S-shaped) dose-response curve
What is a potential adverse effect of thiazide diuretics?
Hypercalcemia
What is the primary use of thiazide diuretics in the treatment of idiopathic hypercalciuria?
To decrease urinary calcium excretion
What is the effect of loop diuretics on urinary calcium excretion?
Increase urinary calcium excretion
Which of the following mechanisms is responsible for the regulation of Ca2+ excretion in the collecting tubule and duct?
Regulation by parathyroid hormone
Which of the following is a characteristic of thiazide diuretics?
They are inexpensive and well tolerated
Which of the following is a consequence of the mechanism of action of thiazide diuretics?
Decreased Na+ reabsorption in the distal convoluted tubule
What is the effect of thiazide diuretics on the body's potassium levels?
They decrease K+ levels in the body
Which of the following is a unique ability of thiazide diuretics?
They decrease urinary calcium excretion
What is the mechanism of action of thiazide-like diuretics?
Inhibition of the Na+/Cl- cotransporter
Which of the following is a therapeutic use of thiazide diuretics?
Mild to moderate essential hypertension
What is the effect of thiazide diuretics on peripheral vascular resistance?
They decrease peripheral vascular resistance
Which of the following is a characteristic of thiazide diuretics?
They have a low ceiling of effect
What is the effect of spironolactone on androgen levels in polycystic ovary syndrome?
Blocks androgen receptors and inhibits steroid synthesis
Which of the following diuretics does not require the presence of aldosterone for its action?
Triamterene
What is the effect of acetazolamide on urinary pH?
Markedly elevates urinary pH
What is the primary use of osmotic diuretics?
To maintain urine flow following acute toxic ingestion of substances
Which of the following is a side effect of triamterene?
Increased uric acid
What is the mechanism of action of spironolactone in the collecting tubule?
Inhibits aldosterone receptors
What is the effect of acetazolamide on phosphate excretion?
Unknown mechanism
Which of the following diuretics is used in the prophylaxis of altitude sickness?
Acetazolamide
What is the effect of spironolactone on potassium levels?
Increases potassium levels
What is the primary mechanism of action of loop diuretics in the treatment of hypercalcemia?
Stimulation of tubular Ca2+ secretion
What is the adverse effect of loop diuretics that is associated with the use of aminoglycoside?
Ototoxicity
What is the effect of potassium-sparing diuretics on the collecting tubule?
Inhibition of Na+ reabsorption and stimulation of K+ excretion
What is the primary indication for the use of aldosterone antagonists in patients with heart failure?
Prevention of myocardial remodeling
What is the effect of loop diuretics on blood volume?
Decrease in blood volume
What is the primary mechanism of action of spironolactone in the collecting tubule?
Antagonism of aldosterone at intracellular cytoplasmic receptor sites
What is the effect of aldosterone antagonists on potassium levels in edematous states?
Increase in potassium levels
What is the therapeutic use of spironolactone in patients with hepatic cirrhosis?
Treatment of edema associated with secondary hyperaldosteronism
What is the adverse effect of loop diuretics that can be corrected by oral supplementation?
Hypomagnesemia
Study Notes
Nephron and Diuretics
- The nephron is the microscopic structural and functional unit of the kidney, composed of the renal corpuscle and renal tubule.
- Diuretics are drugs that increase the volume of urine.
Normal Regulation of Fluid and Electrolytes by the Kidneys
- About 16% to 20% of the blood entering the kidneys is filtered from the glomerular capillaries into Bowman's capsule.
- The filtrate contains glucose, sodium bicarbonate, amino acids, and other organic solutes, as well as electrolytes such as Na+, K+, and Cl−.
Proximal Convoluted Tubule
- Most of the glucose, bicarbonate, and amino acids are reabsorbed in the proximal convoluted tubule.
- Approximately two-thirds of the Na+ is also reabsorbed.
- Water passes passively from the lumen to the blood to maintain osmolar equality.
Descending and Ascending Loops of Henle
- The osmolarity increases along the descending portion of the loop of Henle due to water reabsorption.
- The ascending loop of Henle is impermeable to water, and active reabsorption of Na+, K+, and Cl− is mediated by a Na+/K+/2Cl− cotransporter.
Distal Convoluted Tubule and Collecting Tubule
- The distal convoluted tubule is also impermeable to water.
- About 10% of the filtered sodium chloride is reabsorbed via a Na+/Cl− transporter.
- Calcium reabsorption is mediated by passage through a channel and then transported by a Na+/Ca2+ exchanger into the interstitial fluid.
Thiazides
- Thiazides affect the distal convoluted tubule and have equal maximum diuretic effects.
- They are sometimes called "low ceiling diuretics."
- Examples include chlorothiazide, hydrochlorothiazide, and chlorthalidone.
Mechanism of Action of Thiazides
- Thiazides act mainly in the distal convoluted tubule to decrease the reabsorption of Na+.
- They inhibit a Na+/Cl− cotransporter on the luminal membrane of the tubules.
Actions of Thiazides
- Increased excretion of Na+ and Cl−.
- Loss of K+ and Mg2+.
- Decreased urinary calcium excretion.
- Reduced peripheral vascular resistance.
Therapeutic Uses of Thiazides
- Hypertension.
- Heart failure.
- Hypercalciuria.
- Diabetes insipidus.
Adverse Effects of Thiazides
- Hypokalemia.
- Hypomagnesemia.
- Hyponatremia.
- Hyperuricemia.
- Hypovolemia.
- Hypercalcemia.
- Hyperglycemia.
Loop Diuretics
- Loop diuretics act on the ascending limb of the loop of Henle.
- They have the highest efficacy in mobilizing Na+ and Cl− from the body.
- Examples include furosemide, bumetanide, torsemide, and ethacrynic acid.
Mechanism of Action of Loop Diuretics
- Loop diuretics inhibit the cotransport of Na+/K+/2Cl− in the luminal membrane in the ascending limb of the loop of Henle.
Actions of Loop Diuretics
- Diuresis.
- Venodilation.
- Increased urinary calcium excretion.
Therapeutic Uses of Loop Diuretics
- Edema.
- Hypercalcemia.
- Hyperkalemia.
Adverse Effects of Loop Diuretics
- Ototoxicity.
- Hyperuricemia.
- Acute hypovolemia.
- Potassium depletion.
- Hypomagnesemia.
Potassium-Sparing Diuretics
- Potassium-sparing diuretics act in the collecting tubule to inhibit Na+ reabsorption and K+ excretion.
- Examples include spironolactone and eplerenone.
Mechanism of Action of Potassium-Sparing Diuretics
- Spironolactone antagonizes aldosterone at intracellular cytoplasmic receptor sites.
Actions of Potassium-Sparing Diuretics
- In most edematous states, blood levels of aldosterone are high, causing retention of Na+.
- Spironolactone antagonizes the activity of aldosterone, resulting in retention of K+ and excretion of Na+.
Therapeutic Uses of Potassium-Sparing Diuretics
- Edema.
- Hypokalemia.
- Heart failure.
- Resistant hypertension.
- Polycystic ovary syndrome.
Adverse Effects of Potassium-Sparing Diuretics
- Hyperkalemia.
- Gynecomastia.
Carbonic Anhydrase Inhibitor
- Acetazolamide is a carbonic anhydrase inhibitor that is used for its other pharmacologic actions than for its diuretic effect.
- Mechanism of action: inhibits carbonic anhydrase located intracellularly and on the apical membrane of the proximal tubular epithelium.
Therapeutic Uses of Acetazolamide
- Glaucoma.
- Altitude sickness.
Osmotic Diuretics
- Osmotic diuretics are used to increase water excretion rather than Na+ excretion.
- Examples include mannitol and urea.
- They are used to maintain urine flow following acute toxic ingestion of substances capable of producing acute renal failure.
Nephron and Diuretics
- The nephron is the microscopic structural and functional unit of the kidney, composed of the renal corpuscle and renal tubule.
- Diuretics are drugs that increase the volume of urine.
Normal Regulation of Fluid and Electrolytes by the Kidneys
- About 16% to 20% of the blood entering the kidneys is filtered from the glomerular capillaries into Bowman's capsule.
- The filtrate contains glucose, sodium bicarbonate, amino acids, and other organic solutes, as well as electrolytes such as Na+, K+, and Cl−.
Proximal Convoluted Tubule
- Most of the glucose, bicarbonate, and amino acids are reabsorbed in the proximal convoluted tubule.
- Approximately two-thirds of the Na+ is also reabsorbed.
- Water passes passively from the lumen to the blood to maintain osmolar equality.
Descending and Ascending Loops of Henle
- The osmolarity increases along the descending portion of the loop of Henle due to water reabsorption.
- The ascending loop of Henle is impermeable to water, and active reabsorption of Na+, K+, and Cl− is mediated by a Na+/K+/2Cl− cotransporter.
Distal Convoluted Tubule and Collecting Tubule
- The distal convoluted tubule is also impermeable to water.
- About 10% of the filtered sodium chloride is reabsorbed via a Na+/Cl− transporter.
- Calcium reabsorption is mediated by passage through a channel and then transported by a Na+/Ca2+ exchanger into the interstitial fluid.
Thiazides
- Thiazides affect the distal convoluted tubule and have equal maximum diuretic effects.
- They are sometimes called "low ceiling diuretics."
- Examples include chlorothiazide, hydrochlorothiazide, and chlorthalidone.
Mechanism of Action of Thiazides
- Thiazides act mainly in the distal convoluted tubule to decrease the reabsorption of Na+.
- They inhibit a Na+/Cl− cotransporter on the luminal membrane of the tubules.
Actions of Thiazides
- Increased excretion of Na+ and Cl−.
- Loss of K+ and Mg2+.
- Decreased urinary calcium excretion.
- Reduced peripheral vascular resistance.
Therapeutic Uses of Thiazides
- Hypertension.
- Heart failure.
- Hypercalciuria.
- Diabetes insipidus.
Adverse Effects of Thiazides
- Hypokalemia.
- Hypomagnesemia.
- Hyponatremia.
- Hyperuricemia.
- Hypovolemia.
- Hypercalcemia.
- Hyperglycemia.
Loop Diuretics
- Loop diuretics act on the ascending limb of the loop of Henle.
- They have the highest efficacy in mobilizing Na+ and Cl− from the body.
- Examples include furosemide, bumetanide, torsemide, and ethacrynic acid.
Mechanism of Action of Loop Diuretics
- Loop diuretics inhibit the cotransport of Na+/K+/2Cl− in the luminal membrane in the ascending limb of the loop of Henle.
Actions of Loop Diuretics
- Diuresis.
- Venodilation.
- Increased urinary calcium excretion.
Therapeutic Uses of Loop Diuretics
- Edema.
- Hypercalcemia.
- Hyperkalemia.
Adverse Effects of Loop Diuretics
- Ototoxicity.
- Hyperuricemia.
- Acute hypovolemia.
- Potassium depletion.
- Hypomagnesemia.
Potassium-Sparing Diuretics
- Potassium-sparing diuretics act in the collecting tubule to inhibit Na+ reabsorption and K+ excretion.
- Examples include spironolactone and eplerenone.
Mechanism of Action of Potassium-Sparing Diuretics
- Spironolactone antagonizes aldosterone at intracellular cytoplasmic receptor sites.
Actions of Potassium-Sparing Diuretics
- In most edematous states, blood levels of aldosterone are high, causing retention of Na+.
- Spironolactone antagonizes the activity of aldosterone, resulting in retention of K+ and excretion of Na+.
Therapeutic Uses of Potassium-Sparing Diuretics
- Edema.
- Hypokalemia.
- Heart failure.
- Resistant hypertension.
- Polycystic ovary syndrome.
Adverse Effects of Potassium-Sparing Diuretics
- Hyperkalemia.
- Gynecomastia.
Carbonic Anhydrase Inhibitor
- Acetazolamide is a carbonic anhydrase inhibitor that is used for its other pharmacologic actions than for its diuretic effect.
- Mechanism of action: inhibits carbonic anhydrase located intracellularly and on the apical membrane of the proximal tubular epithelium.
Therapeutic Uses of Acetazolamide
- Glaucoma.
- Altitude sickness.
Osmotic Diuretics
- Osmotic diuretics are used to increase water excretion rather than Na+ excretion.
- Examples include mannitol and urea.
- They are used to maintain urine flow following acute toxic ingestion of substances capable of producing acute renal failure.
Learn about the structure and function of nephrons, the microscopic units of the kidney, and how diuretics affect the volume of urine. Understand the normal regulation of fluid and electrolytes by the kidneys.
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