Pharm Diuretics

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  • 1/20 Questions

    A 65-year-old man was found to have a plasma level of calcium of 12.2 mg/dL. during a followup visit. The man, who had been suffering from Hodgkin’s lymphoma for three years, was recently diagnosed with nephrolithiasis and started a therapy with hydrochlorothiazide three weeks previously. Which of the following statements best explains the most likely mechanism of thiazide induced hypercalcemia?

    • Enhancement of Na+/Ca++ exchanger in the distal tubule
    • Increased Ca++ reabsorption in the proximal tubule
    • Decreased secretion of parathyroid hormone
    • Decreased renal excretion of Vit D
    • Enhancement of Na+/K+/ 2Cl symport
    • Increased glomerular filtration of Ca++
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About This Quiz

This quiz titled 'Pharm diuretics' assesses knowledge of various diuretics, their mechanisms, and clinical applications. It is designed for medical students and professionals to understand drug actions in scenarios like congestive heart failure and their molecular interactions.

Pharm Diuretics - Quiz

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  • 2. 

    A 69-year-old depressed man, who has been suffering from glaucoma for ten years, was admitted to the emergency room after he took several tablets of one of his medications in a suicide attempt. The patient was drowsy an complained of nausea, paresthesias and tiredness. Physical examination disclosed an erythematous skin eruption and lab exams showed hyperchloremic metabolic acidosis. Which of the following medications might have caused the patient’s these symptoms?

    • Mannitol

    • Latanoprost

    • Timolol

    • Acetazolamide

    • Pilocarpine

    Correct Answer
    A. Acetazolamide
    Explanation
    Learning objective: describe the main adverse effects of carbonic anhydrase inhibitors.
    Answer: D
    The symptoms of the patients are classic symptoms of acetazolamide overdose. The drug is
    used for glaucoma because it decreases the production of aqueous humor, a fluid which is rich
    in bicarbonate. High doses of carbonic anhydrase inhibitors like acetazolamide can cause
    metabolic acidosis since they profoundly increase the urinary excretion of bicarbonate. Because
    the plasma loss of bicarbonate is counterbalanced by an in crease of extracellular Cl-, most
    metabolic acidosis are hyperchloremic.
    A, B, C, E) All these listed drugs are used for glaucoma, but they do not cause hyperchloremic
    metabolic acidosis.

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  • 3. 

    Directions: questions 1-5 Match each diuretic with the appropriate description (each lettered option can be selected once, more than once, or not at all): This drug inhibits Na+ reabsorption in the proximal tubule

    • Acetazolamide

    • Amiloride

    • Conivaptan

    • Ethacrynic acid

    • Indapamide

    • Mannitol

    • Spironolactone

    • Triamterene

    Correct Answer
    A. Acetazolamide
    Explanation
    Acetazolamide is a diuretic that inhibits the reabsorption of sodium in the proximal tubule of the kidney. This action prevents the reabsorption of water, leading to increased urine production. Acetazolamide is commonly used to treat conditions such as glaucoma, altitude sickness, and certain types of epilepsy.

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  • 4. 

    A 55-year-old alcoholic man was admitted to the hospital because of disorientation, amnesia, confusion and bizarre behavior of 24 hour duration. His wife reported that the man was under therapy for hypertension and for a recently diagnosed glaucoma. Physical examination revealed a cachectic male in a confused mental state. Abdomen appeared tense with prominent veins and ascites and a musty ,pungent odor was noted in his breath. Neurological sings included nystagmus, ataxia and asterixis. Which of the following drugs most likely triggered the patient’s syndrome?

    • Acetazolamide

    • Nifedipine

    • Losartan

    • Timolol

    • Lovastatin

    Correct Answer
    A. Acetazolamide
    Explanation
    Learning objective: describe the main adverse effects of carbonic anhydrase inhibitors.
    Answer: A
    The history, the symptoms and signs of the patient suggest that he was suffering from
    portal-systemic encephalopathy, a syndrome that can occur when extensive portal-systemic
    collaterals have developed as a result of portal hypertension. Liver cirrhosis is one of the most
    common causes of portal-systemic encephalopathy, and this was most likely the cause in the
    present case. Carbonic anhydrase inhibitors cause urine alkalinization which in turn reduces
    urinary excretion of ammonia. The resulting hyperammonemia is an important cause of portasystemic
    encephalopathy, since NH 4+ causes brain toxicity. Likely the ophthalmologist
    overlooked the possible cirrhosis of the patient and prescribed acetazolamide for glaucoma.
    B, C, D, E) These drugs do not trigger liver encephalopathy in patient at risk.

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  • 5. 

    Directions: questions 1-5 Match each diuretic with the appropriate description (each lettered option can be selected once, more than once, or not at all): This drug causes an initial extracellular volume expansion in normal subjects

    • Acetazolamide

    • Amiloride

    • Conivaptan

    • Ethacrynic acid

    • Indapamide

    • Mannitol

    • Spironolactone

    • Triamterene

    Correct Answer
    A. Mannitol
    Explanation
    Mannitol is a diuretic that causes an initial extracellular volume expansion in normal subjects.

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  • 6. 
    A 27-year-old woman with a history of high altitude sickness was placed on prophylactic treatment with a diuretic drug prior to going on a hiking trip to the Rocky Mountains. Which of the following urine electrolyte profiles is most consistent with this drug treatment?(+ increased in urine; - decreased in urine; 0 no change in urine) - ProProfs

    A 27-year-old woman with a history of high altitude sickness was placed on prophylactic treatment with a diuretic drug prior to going on a hiking trip to the Rocky Mountains. Which of the following urine electrolyte profiles is most consistent with this drug treatment?(+ increased in urine; - decreased in urine; 0 no change in urine)

    • A

    • B

    • C

    • D

    • E

    Correct Answer
    A. A
    Explanation
    Learning objective: describe the urine profile of a patient treated with carbonic anhydrase
    inhibitors
    Answer: A
    Acetazolamide, a carbonic anhydrase inhibitor, is the only diuretic used to prevent mountain
    sickness in persons who are at risk for this disorder and have to go to a high altitude. The
    mechanism of this action is not clear but it may be related to the induction of metabolic acidosis.
    Carbonic anhydrase inhibitors produce an urine which is very rich in bicarbonate. Urinary
    sodium is only slightly increased (the efficacy of these diuretic is low). Urinary K+ excretion is
    also increased (all diuretics, but potassium sparing diuretics increase urinary K+ excretion).
    B) This urine profile would be caused by osmotic diuretic
    C) This urine profile would be caused by thiazides
    D) This urine profile would be caused by loop diuretics
    E) This urine profile would be caused by K+ sparing diuretic

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  • 7. 

    A 67-year-old man was found to have a plasma level of calcium of 12.2 mg/dL. during a followup visit. The man, who had been suffering from Hodgkin’s lymphoma for three years, was recently diagnosed with nephrolithiasis and started a therapy with hydrochlorothiazide three weeks previously. Which of the following statements best explains the most likely mechanism of thiazide induced hypercalcemia?

    • Enhancement of Na+/Ca++ exchanger in the distal tubule

    • Increased Ca++ reabsorption in the proximal tubule

    • Decreased secretion of parathyroid hormone

    • Decreased renal excretion of Vit D

    • Enhancement of Na+/K+/ 2Cl symport

    • Increased glomerular filtration of Ca++

    Correct Answer
    A. Enhancement of Na+/Ca++ exchanger in the distal tubule
    Explanation
    Learning objective: explain the mechanism of thiazides induced hypercalcemia.
    Answer: A
    In the kidney, the distal convolute tubule reabsorbs about 8% of the filtered Ca++ load. This
    reabsorption occurs through epithelial Ca++ channels. In the steady state however the cell must
    extrude all the entered Ca++ and this occurs through a plasma membrane Ca++ ATPase (the
    Ca++ pump) and also through a Na+/Ca++ exchanger located on the basolateral surface of cells
    of the distal tubule. Thiazides inhibit the Na+/Cl- symport in the early distal convolute tubule, so
    decreasing the intracellular concentration of Na. This likely enhances the activity of the
    Na+/Ca++ exchanger which in turn creates a greater driving force for reabsorption of Ca++
    through the epithelial Ca++ channels. The final effect is an increased reabsorption of Ca++ that
    can cause hypercalcemia or, more often, can unmask hypercalcemia due to other causes , like
    in the present case (malignancy is a common cause of hypercalcemia).
    B, C, D, E, F) Thiazides do not cause these effects.

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  • 8. 

    A 63-year-old man with a long history of heart failure was admitted to the hospital because of severe dyspnea and edema on legs, thighs and lower abdominal wall. Pertinent lab results on admission included a GFR of 25 mL/min. A diuretic with which of the following mechanism of action would be appropriate to relieve the edema of this patient?

    • Blockade of Na+ reabsorption in the proximal tubule

    • Blockade of Na+ channels in the collecting tubule

    • Blockade of Na+/K+/2Cl- symport in the Henle’s loop

    • Inhibition of aldosterone actions in the collecting tubule

    • Blockade of Na+/Cl- symport in the early distal tubule

    Correct Answer
    A. Blockade of Na+/K+/2Cl- symport in the Henle’s loop
    Explanation
    Learning objective: explain the molecular mechanism of action of loop diuretics.
    Answer: C
    When the GFR is less than 30 mL/min (as it can occur in case of severe heart failure) the only
    diuretics that are still active are loop diuretics. This is likely related, at least in part, to the fact
    that, by inhibiting NA+ and Cl- transport into the macula densa, the macula densa is no longer
    able to sense salt concentration in the tubular fluid, and therefore increases renin secretion
    leading to an increase in angiotensin II. Because angiotensin II preferentially constricts the
    efferent arteriole, GFR is enhanced.
    A, B, D, E) (see explanation above)

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  • 9. 

    A 54-year-old woman recently diagnosed with open angle glaucoma was prescribed topical timolol. Two weeks later the intraocular pressure was decreased but was still above the normal value. The ophthalmologist decided to add another topical drug that act by decreasing aqueous humor production. Which of the following drugs was most likely prescribed?

    • Pilocarpine

    • Carbachol

    • Latanoprost

    • Dorzolamide

    • Mannitol

    Correct Answer
    A. Dorzolamide
    Explanation
    Learning objective: describe the main therapeutic uses of carbonic anhydrase inhibitors.
    Answer: D
    Dorzolamide is a carbonic anhydrase inhibitors. The rationale of the use of these drugs in open
    angle glaucoma is based on the fact that aqueous humor is rich in bicarbonate. By inhibiting
    bicarbonate synthesis, the production of aqueous humor is decreased.
    A, B, C, E) All these drugs are used in glaucoma but they act by increasing the outflow, not by
    decreasing the production, of the aqueous humor

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  • 10. 

    A 56-year old woman recently diagnosed with congestive heart failure, started a therapy which included furosemide. Acetazolamide was also added to counteract the potential metabolic alkalosis induced by furosemide. Which of the following molecular actions most likely mediated the therapeutic effect of acetazolamide in this patient?

    • Inhibition of carbonic acid dehydration in the tubular lumen

    • Stimulation of bicarbonate reabsorption in the proximal tubule

    • Inhibition of Na+ reabsorption in the early distal tubule

    • Stimulation of H+ reabsorption in the proximal tubule

    • Stimulation of carbonic acid formation - inside the tubular cells

    Correct Answer
    A. Inhibition of carbonic acid dehydration in the tubular lumen
    Explanation
    Learning objective: explain the molecular mechanism of diuretic action of carbonic
    anhydrase inhibitors.
    Answer: A
    Carbonic anhydrase is an enzyme located in the brush border and in the cytoplasm of the cells
    of proximal convolute tubule. In the proximal tubule a large amount of H+ is secreted into the
    lumen via a Na+/H+ exchanger. Most of this H+ combines with bicarbonate ion in the tubular
    fluid to form carbonic acid which is rapidly dehydrated to CO2 and water (this reaction is
    catalyzed by carbonic anhydrase). The CO2 diffuses into the proximal tubular cells where the
    opposite reaction takes places to form H+ and HCO3 (this reaction too is catalyzed by carbonic
    -
    anhydrase). The HCO3 exits the cell on the basolateral side and is therefore reabsorbed as
    -
    bicarbonate. Hydrogen ion is secreted into the lumen via the Na+/H+ exchanger. Acetazolamide
    is a carbonic anhydrase inhibitor. By blocking the enzyme it blocks the reabsorption of
    bicarbonate and Na+ , resulting in an increase in diuresis.
    B) Acetazolamide cause an inhibition, not a simulation of bicarbonate reabsorption.
    C) This would be the mechanism of action of thiazides.
    D) hydrogen is not reabsorbed by the kidney . By inhibiting carbonic anhydrase, acetazolamide
    inhibits the formation of carbonic acid inside the tubular cells, which in turn inhibits the secretion
    of hydrogen into the lumen.
    E) Acetazolamide cause an inhibition, not a stimulation, of carbonic acid formation inside the
    tubular cells.

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  • 11. 

    Directions: questions 1-5 Match each diuretic with the appropriate description (each lettered option can be selected once, more than once, or not at all): This drug inhibits the synthesis of new Na+ channels in the collecting duct

    • Acetazolamide

    • Amiloride

    • Conivaptan

    • Ethacrynic acid

    • Indapamide

    • Mannitol

    • Spironolactone

    • Triamterene

    Correct Answer
    A. Spironolactone
    Explanation
    Spironolactone is the correct answer because it is a potassium-sparing diuretic that works by inhibiting the synthesis of new Na+ channels in the collecting duct. This action prevents the reabsorption of sodium and water, leading to increased urine production and decreased fluid retention.

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  • 12. 

    Directions: questions 1-5 Match each diuretic with the appropriate description (each lettered option can be selected once, more than once, or not at all): This drug competitively blocks ADH receptors

    • Acetazolamide

    • Amiloride

    • Conivaptan

    • Ethacrynic acid

    • Indapamide

    • Mannitol

    • Spironolactone

    • Triamterene

    Correct Answer
    A. Conivaptan
    Explanation
    Conivaptan is the correct answer because it competitively blocks ADH receptors. The other diuretics listed do not have this specific mechanism of action. Acetazolamide is a carbonic anhydrase inhibitor, Amiloride and Triamterene are potassium-sparing diuretics, Ethacrynic acid is a loop diuretic, Indapamide is a thiazide-like diuretic, Mannitol is an osmotic diuretic, and Spironolactone is an aldosterone antagonist.

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  • 13. 

    Directions: questions 1-5 Match each diuretic with the appropriate description (each lettered option can be selected once, more than once, or not at all): This drug increases the renal reabsorption of Ca++

    • Acetazolamide

    • Amiloride

    • Conivaptan

    • Ethacrynic acid

    • Indapamide

    • Mannitol

    • Spironolactone

    • Triamterene

    Correct Answer
    A. Indapamide
    Explanation
    Indapamide is the correct answer because it is a diuretic that increases the renal reabsorption of Ca++. Acetazolamide, Amiloride, Conivaptan, Ethacrynic acid, Mannitol, Spironolactone, and Triamterene do not have this specific effect.

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  • 14. 

    A 67-year old woman was found to have a plasma level of potassium 3.8 mEq/L during a followup visit. The woman, recently diagnosed with essential hypertension, started a therapy with hydrochlorothiazide one month previously. Which of the following actions most likely contributed to the thiazide-induced increase of renal excretion of potassium?

    • Increased Na+ load in the lumen of the collecting tubule

    • Blockade of Na+/K+/2Cl- cotransporter

    • Thiazide-induced decrease in renal secretion of uric acid

    • Stimulation of Na+/K+ pump

    • Decreased delivery of bicarbonate to the collecting duct

    Correct Answer
    A. Increased Na+ load in the lumen of the collecting tubule
    Explanation
    Learning objective: explain the mechanism of thiazide-induced increase of renal excretion
    of potassium
    Answer: A
    Potassium secretion by the distal tubule is a passive process that depends on the
    electrochemical gradient between the distal tubular cells an the tubular lumen. The higher the
    NA+ load in the distal tubule, the higher NA+ reabsorption. This creates a lumen negative
    potential which favors K+ excretion.
    B) Thiazides do not inhibit this cotransporter.
    C) Thiazide can decrease the secretion of uric acid but this has nothing to do with the thiazide
    induced increase in K+ excretion.
    D) Thiazide do not stimulate the Na+/K+ pump.
    E) Thiazides are weak carbonic anhydrase inhibitors and therefore tend to increase, not to
    decrease, the delivery of bicarbonate to the collecting duct.

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  • 15. 

    A 78-year-old man from a nursing home presented to the emergency room with a change in his mental state over the past few hours. He had a medical history of angina and hypertension presently treated with isosorbide mononitrate, losartan and hydrochlorothiazide. Physical examination showed a person with decreased skin turgor, disorientation to time and place, without focal neurologic deficits. Blood pressure was 110/65 mm Hg on standing and 140/88 mm Hg on laying. Pertinent blood tests on admission were: Na 116 q/L, K 3.1 mEq/L, uric acid 10.2 mg/dL, creatinine 3.7 mg/dL. The physician thought that the syndrome was due to diuretic therapy. Which of the following drug-induced adverse effects most likely caused the patient’s symptoms and signs ?

    • Kidney insufficiency

    • Hypokalemia

    • Hypovolemic hyponatremia

    • Hyperuricemia

    • Hypervolemic hyponatremia

    Correct Answer
    A. Hypovolemic hyponatremia
    Explanation
    Learning objective: explain the mechanism of thiazide-induced extracellular volume depletion.
    Answer: C
    The patient symptoms and signs suggest the diagnosis of hypovolemic hyponatremia which is a
    rare (but sometimes fatal) adverse effects of thiazide diuretics. These drugs affect the diluting
    ability of the kidney while increasing Na+ excretion. Once volume depletion occurs, the release
    of ADH cause water retention and worsens hyponatremia. This effect of thiazides may last 1-2
    weeks after cessation of the therapy. Elderly patients are especially prone to thiazide-induced
    hyponatremia, particularly if a preexisting renal insufficiency exists, like in the present case (see
    high creatinine level).
    A, B, D) These disorders do not cause the symptoms and signs showed by the patient.
    E) The patient is hyponatremic, but the postural hypotension and the diuretic therapy indicate
    that hyponatremia is hypovolemic, not hypervolemic

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  • 16. 

    A 42-year-old obese female was hospitalized because of hypokalemia despite a daily administration of potassium supplement. Laboratory tests upon admission revealed metabolic alkalosis. The patient admitted taking furosemide tablets in an effort to loose weight. Which of the following actions might contribute to furosemide-induced metabolic alkalosis in this patient?

    • The increased reabsorption of uric acid

    • The increase delivery of Na+ to the distal tubule

    • The mild inhibition of carbonic anhydrase

    • The decreased reabsorption of Ca++ in Henle’s loop

    • The inhibition of renin secretion

    Correct Answer
    A. The increase delivery of Na+ to the distal tubule
    Explanation
    Learning objective: explain the molecular mechanism of furosemide-induced metabolic
    alkalosis.
    Answer: B
    There are three main causes of alkalosis induced by loop diuretics. The most important is the
    increase delivery of Na+ to the distal tubule. The consequent increased reabsorption of Na+
    creates a luminal negative potential which favors both H+ and K+ excretion. The second cause
    is the stimulation of aldosterone release due to volume contraction and increased renin
    secretion. The third cause can occur only when hypokalemia is severe. In this case K+ tends to
    leave the cell and H+ enters to maintain electroneutrality with the final result of extracellular
    alkalosis and intracellular acidosis.
    A, C, D,) All these are action of loop diuretics but these actions do not lead to metabolic
    alkalosis
    E) Loop diuretics actually increase renin secretion.

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  • 17. 

    A 66-year-old woman suffering from systolic cardiac failure was brought to the emergency room because of a sudden onset of extreme dyspnea. She presented with cyanosis, tachypnea, hyperpnea, restlessness, anxiety and a sense of suffocation. Cough was prominent and produced pink-tinged, frothy sputum. Pulse was thready and fast (120 bpm), blood pressure 80/45 mm Hg and rales were audible at the lung bases. Which of the following drugs was most likely included in the immediate medical treatment of this patient?

    • Hydrochlorothiazide

    • Amiloride

    • Mannitol

    • Epinephrine

    • Furosemide

    • Metoprolol

    Correct Answer
    A. Furosemide
    Explanation
    Learning objective: describe the main therapeutic uses of loop diuretics.
    Answer: E
    The patient exhibits the classic symptoms of pulmonary edema. Furosemide is the diuretic of
    first choice for this condition because it is able to quickly reduce preload (and therefore the left
    ventricular filling pressure) through the following actions:
    a) A rapid increase in venous capacitance, likely mediated by prostaglandin release.(the initial
    beneficial effect may result more from this action than from diuresis).
    b) A brisk and abundant natriuresis
    A, B) These diuretics are less effective than loop diuretics and do not have acute vasodilating
    properties.
    C, D, F) These drugs are contraindicated in pulmonary edema

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  • 18. 

    A 76-year-old woman from a nursing home presented to the emergency room with a change in her mental state over the past few hours. She had a medical history of coronary artery disease and hypertension. Her medications included aspirin, captopril , lovastatin and a diuretic. On physical examination she showed a decreased skin turgor, orthostatic hypotension, disorientation to time, place and person, without focal neurologic deficits. Pertinent blood test results on admission were Na 125 mEq/L, creatinine 2.7 mg/dL. Which of the following drugs most likely caused the patient syndrome?

    • Captopril

    • Spironolactone

    • Lovastatin

    • Triamterene

    • Acetazolamide

    • Indapamide

    Correct Answer
    A. Indapamide
    Explanation
    Learning objective: identify the diuretics that can cause hyponatremia.
    Answer: F
    The patient symptoms and signs suggest the diagnosis of dilutional hyponatremia, which is a
    rare (but sometimes fatal) adverse effect of thiazide diuretics. These drugs affect the diluting
    ability of the kidney while increasing Na+ excretion. Once volume depletion occurs the release
    of ADH cause water retention and worsens the hyponatremia. In contrast loop diuretics (not
    shown in the question) affect also the concentrating ability of the kidney so limiting the ADH
    mediated water retention. The effect of thiazides may last 1-2 weeks after cessation of the
    therapy. Elderly patients are especially prone to thiazide-induced hyponatremia, particularly if a
    preexisting renal insufficiency exists, like in the present case (see high creatinine level).
    A, B, C, D, E) The risk of dilutional hyponatremia with these drugs is negligible.

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  • 19. 
    A 47-year-old woman suffering from metastatic breast cancer was admitted to the hospital because of a persistent thirst and polyuria. Admission lab data were: serum K 2.8 mEq/L, Ca 16.2 mg/dL, Na 155 mEq/L. Urinalysis: specific gravity 1.001, osmolality 80 mOsm/L (range 50-1440), protein and microscope negative. The patient was given a water deprivation test: all fluids were withheld until serum osmolality increased into the hyperosmolar range (> 310), then 5 units of vasopressin were given SC. Results are tabulated below:   Which of the following drugs would be most appropriate to treat the patient’s condition? - ProProfs

    A 47-year-old woman suffering from metastatic breast cancer was admitted to the hospital because of a persistent thirst and polyuria. Admission lab data were: serum K 2.8 mEq/L, Ca 16.2 mg/dL, Na 155 mEq/L. Urinalysis: specific gravity 1.001, osmolality 80 mOsm/L (range 50-1440), protein and microscope negative. The patient was given a water deprivation test: all fluids were withheld until serum osmolality increased into the hyperosmolar range (> 310), then 5 units of vasopressin were given SC. Results are tabulated below:   Which of the following drugs would be most appropriate to treat the patient’s condition?

    • Desmopressin

    • Hydrochlorothiazide

    • Demeclocycline

    • Amiloride

    • Furosemide

    Correct Answer
    A. Hydrochlorothiazide
    Explanation
    Learning objective: describe the therapeutic use of thiazides in diabetes insipidus.
    Answer: B
    Polyuria with low urine osmolality suggests the diagnosis of diabetes insipidus. To determine the
    cause of this syndrome vasopressin is used. Nephrogenic diabetes insipidus is vasopressinresistant,
    so that urine osmolality would not change significantly after vasopressin, as in the
    present case. A common cause of nephrogenic diabetes insipidus is hypercalcemia which is
    common in bone metastases of various tumors. Thiazide diuretics can reduce polyuria and
    polydipsia in diabetes insipidus. The mechanism of this paradoxical effect is related to
    the extracellular volume reduction which in turn causes an enhanced proximal reabsorption of
    NA+ and water in the proximal tubule and a decrease delivery of fluid to the distal tubule. Thus
    the maximum volume of dilute urine that can be produced is lowered.
    A) Desmopressin is effective in neurogenic diabetes insipidus but is ineffective in nephrogenic
    diabetes insipidus. Neurogenic diabetes insipidus is unlikely because it is vasopressin-sensitive
    and therefore urine osmolality would have been increased significantly after vasopressin.
    C) Demeclocycline is appropriate in case of the syndrome of inappropriate ADH secretion. This
    syndrome leads to hyponatremia (not hypernatremia, like in diabetes insipidus) and low serum
    osmolality.
    D) Amiloride is used effectively in case of lithium-induced nephrogenic diabetes insipidus
    because the drug blocks lithium transport into the cells of the collecting tubule. However it is not
    effective in other forms of diabetes insipidus.
    E) Furosemide is not effective in nephrogenic diabetes insipidus. It can be used in case of
    chronic renal failure but this diagnosis is unlikely in the present case because the urine
    osmolality is lower than serum osmolality (in chronic renal failure urine osmolality is usually fixed
    close to that of serum).

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  • 20. 

    A 15-year-old boy awoke with weakness and an hour later realized he could not move his legs. The attack lasted about 2 hours, then it disappeared without residual symptoms. The boy was referred to a neurologic clinic where the diagnosis of familial hypokalemic periodic paralysis was made. He was prescribed potassium chloride and a diuretic that is able to prevent the attacks in many cases. Which of the following drugs was most likely prescribed?

    • Mannitol

    • Hydrochlorothiazide

    • Ethacrynic acid

    • Triamterene

    • Acetazolamide

    Correct Answer
    A. Acetazolamide
    Explanation
    Learning objective: describe the main therapeutic uses of carbonic anhydrase inhibitors.
    Answer: E
    Familial hypokalemic periodic paralysis is a rare autosomal condition characterized by episodes
    of flaccid paralysis with loss of deep tendon reflex. Potassium flows from the bloodstream into
    muscle cells during attacks. Acetazolamide may help to prevent the attacks; the mechanism of
    action is still uncertain, but it could be related to the production of metabolic acidosis which
    decreases the activity of Na+/K+ ATPase, so lowering the entry of potassium into muscle cells.
    A, B, C) These diuretics can cause hypokalemia and therefore are contraindicated in this
    disease.
    D) Potassium sparing diuretics are sometimes used in hypokalemic periodic paralysis but they
    are not needed in this case since a potassium supplementation was prescribed.

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Quiz Review Timeline (Updated): Mar 22, 2023 +

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  • Current Version
  • Mar 22, 2023
    Quiz Edited by
    ProProfs Editorial Team
  • Jul 08, 2012
    Quiz Created by
    Chachelly

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